`briefcase build` intermittent failure (not an ELF file?)

[rachelkelly]

Describe the bug Command briefcase build sometimes needs multiple runs to build entirely (and sometimes will not build at all).

To Reproduce Steps to reproduce the behavior:

1. Hello World tutorial for linux, pages 1-3. Have to build it twice, due to "Error while building app helloworld" (Apologies I've lost the output of these unsuccessful builds because they worked afterward & I just kept moving)
2. Run briefcase build again! Then it works
3. Hope the same behavior persists - maybe it just needs a twofer. However, after trying to use briefcase build (right before using briefcase run -u on page 4), it simply won't build and throws an error. Therefore, it won't update because the new package is not yet built.

Expected behavior Successful briefcase build in tutorial on Linux KDE Ubuntu 20.04.

Screenshots Scroll to last ~100 lines or so, particularly the not an ELF file bit:

(beeware) rachel@pothos:~/beeware-tutorial/helloworld$ briefcase build

[helloworld] Building AppImage...

[helloworld] Entering Docker context...
linuxdeploy version 1-alpha (git commit ID 8663e5b), Travis build 477 built on 2020-08-07 23:09:55 UTC

-- Creating basic AppDir structure -- 
Creating directory /app/Hello World/Hello World.AppDir/usr/bin/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/lib/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/applications/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/icons/hicolor/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/icons/hicolor/16x16/apps/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/icons/hicolor/32x32/apps/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/icons/hicolor/64x64/apps/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/icons/hicolor/128x128/apps/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/icons/hicolor/256x256/apps/ 
Creating directory /app/Hello World/Hello World.AppDir/usr/share/icons/hicolor/scalable/apps/ 

-- Deploying dependencies for existing files in AppDir -- 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/bin/python3.8 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libpthread.so.0 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libdl.so.2 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libutil.so.1 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libm.so.6 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libc.so.6 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libXau.so.6 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libbz2.so.1.0 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libcrypto.so.1.0.0 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libxcb-render.so.0 
Skipping deployment of blacklisted library /usr/lib/x86_64-linux-gnu/libxcb.so.1 
Deploying shared library /usr/lib/x86_64-linux-gnu/libXau.so.6
Deploying copyright files for file /usr/lib/x86_64-linux-gnu/libXau.so.6 
Deploying shared library /usr/lib/x86_64-linux-gnu/libXdmcp.so.6
Deploying copyright files for file /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libpixman-1.so.0 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libXdmcp.so.6 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libcairo-gobject.so.2 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libcairo.so.2
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libcairo.so.2 using dpkg-query 
Skipping deployment of blacklisted library /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libglib-2.0.so.0 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libpixman-1.so.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libpixman-1.so.0 using dpkg-query 
Skipping deployment of blacklisted library /usr/lib/x86_64-linux-gnu/libfontconfig.so.1 
Skipping deployment of blacklisted library /usr/lib/x86_64-linux-gnu/libfreetype.so.6 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libpng12.so.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libpng12.so.0 using dpkg-query 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libxcb-shm.so.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libxcb-shm.so.0 using dpkg-query 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libxcb-render.so.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libxcb-render.so.0 using dpkg-query 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libXrender.so.1
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libXrender.so.1 using dpkg-query 
Skipping deployment of blacklisted library /usr/lib/x86_64-linux-gnu/libX11.so.6 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libXext.so.6
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libXext.so.6 using dpkg-query 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libz.so.1 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/librt.so.1 
Deploying shared library /usr/lib/x86_64-linux-gnu/libffi.so.6
Deploying copyright files for file /usr/lib/x86_64-linux-gnu/libffi.so.6 
Deploying shared library /lib/x86_64-linux-gnu/libpcre.so.3
Deploying copyright files for file /lib/x86_64-linux-gnu/libpcre.so.3 
Skipping deployment of blacklisted library /lib/x86_64-linux-gnu/libexpat.so.1 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libgdbm.so.3 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libXrender.so.1 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libsqlite3.so.0 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libnsl.so.1 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libgdbm_compat.so.3 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libgdbm.so.3
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libgdbm.so.3 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_decimal.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_sqlite3.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libsqlite3.so.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libsqlite3.so.0 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/zlib.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/grp.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/fcntl.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_xxtestfuzz.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/cmath.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_codecs_tw.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_crypt.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libcrypt.so.1
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libcrypt.so.1 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/audioop.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/binascii.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/select.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_opcode.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_asyncio.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_codecs_jp.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/math.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/nis.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libnsl.so.1
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libnsl.so.1 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_hashlib.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libcrypto.so.1.0.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libcrypto.so.1.0.0 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_xxsubinterpreters.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_lsprof.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/spwd.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_codecs_cn.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_gdbm.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libgdbm.so.3
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libgdbm.so.3 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_pickle.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_blake2.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/ossaudiodev.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_bisect.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/pyexpat.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_queue.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_sha1.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_codecs_hk.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/syslog.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_contextvars.cpython-38-x86_64-linux-gnu.so 
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Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/mmap.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/resource.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_struct.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_statistics.cpython-38-x86_64-linux-gnu.so 
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Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_lzma.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../liblzma.so.5
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../liblzma.so.5 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_heapq.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_ssl.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libssl.so.1.0.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libssl.so.1.0.0 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_socket.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_datetime.cpython-38-x86_64-linux-gnu.so 
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Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_bz2.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libbz2.so.1.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libbz2.so.1.0 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_sha512.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_codecs_kr.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_ctypes.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libffi.so.6
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libffi.so.6 using dpkg-query 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/_dbm.cpython-38-x86_64-linux-gnu.so 
Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libgdbm_compat.so.3
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/python3.8/lib-dynload/../../libgdbm_compat.so.3 using dpkg-query 
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Deploying shared library /app/Hello World/Hello World.AppDir/usr/lib/libcrypto.so.1.0.0
WARNING: Could not find copyright files for file /app/Hello World/Hello World.AppDir/usr/lib/libcrypto.so.1.0.0 using dpkg-query 
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Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/lib/libcrypt.so.1 
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-- Deploying dependencies only for ELF files -- 
Deploying files in directory /app/Hello World/Hello World.AppDir/usr/app_packages/cairo 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/cairo/__init__.pyi 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/cairo/__init__.py 
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Deploying dependencies for ELF file in AppDir: /app/Hello World/Hello World.AppDir/usr/app_packages/cairo/_cairo.cpython-38-x86_64-linux-gnu.so 
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Deploying files in directory /app/Hello World/Hello World.AppDir/usr/app_packages/gi 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_signalhelper.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_ossighelper.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_error.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/docstring.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/importer.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/pygtkcompat.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_gtktemplate.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_compat.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_constants.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/types.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/module.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_option.py 
WARNING: Not an ELF file: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/__init__.py 
Deploying dependencies for ELF file in AppDir: /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_gi.cpython-38-x86_64-linux-gnu.so 
Deploying dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_gi.cpython-38-x86_64-linux-gnu.so 
ERROR: Could not find dependency: libffi.so.7 
WARNING: Failed to deploy dependencies for ELF file /app/Hello World/Hello World.AppDir/usr/app_packages/gi/_gi.cpython-38-x86_64-linux-gnu.so, skipping 

Error while building app helloworld.
(beeware) rachel@pothos:~/beeware-tutorial/helloworld$ 

Environment:

• Operating System: Kubuntu 20.04
• Python version: 3.8.2
• Software versions:
  • Briefcase: 0.3.3
  • Toga:
  • ...

Additional context reminder, just getting this from the Tutorial

[freakboy3742]

Thanks for the report. The "Not an ELF file" message isn't anything to be concerned about; it's only the "Could not find dependency" that is a problem.

I'm a little confused about the sequence of events that leads to you getting this error, though. Are you saying that you are:

• running through the tutorial as scripted
• getting to the first briefcase build
• that build fails
• immediately running briefcase build again
• that build succeeds

You're also saying that this is happening on step 3 of the tutorial, when you do the first run; and on step 4 when you do the explicit code update?

If you're able to show us a log of a successful build, that would also help. The log you've provided has two interesting features:

• After entering the Docker context at the start, it doesn't appear to be unpacking linuxdeploy (which is what it should be doing). I'm interested to know if this is an indication of the source of the failure, or only a quirk of linuxdeploy operating on your machine.
• The cause of the error is that it is searching for libffi.so.7 - which is a library that exists on Ubuntu 20.04, but not on Ubuntu 16.04 (which is the Docker context in which it should be building). The fact that it's referencing libffi.so.7 at all is a very solid indicator that something is going wrong... I'm just not sure what.

Seeing a successful log might help narrow down what is going on.

Two last things to confirm that you're not doing. These are "Hail Mary" questions; I doubt they're the cause, but if you're doing either of these things, it would explain the behavior you're reporting:

1. You're definitely running this in "docker mode"? (i.e., you haven't being using the --no-docker option an leaving that out of the log transcript?)

2. You're using the stock linux support package - currently Python-3.8-linux-x86_64-support.b2.tar.gz - obtained from briefcase itself, rather than anything self compiled? If you're not sure which support package is used, you can look in ~/.briefcase/support; the support packages should be stored there.

[rachelkelly]

Ok, I did this process a few more times in a row just to iron out all the process kinks, and I'm going to chalk this up to newness to the docs. Also, I think, newness to py3-style environmenting, which is the only thing I can guess for the difference in the python - I am one of those unfortunate souls very much stuck on py2 at work, while we move toward py3 slowly, and I am extremely accustomed to virtualenvwrapper's workflow. So I'll do a little reading on py3's venv. Also I think I bungled a couple of mac vs linux instructions in round 1.

It's working great :) thank you @freakboy3742 & sorry to take yr time! Can't wait to have built this idea I have!

[freakboy3742]

Great to hear it's worked out. If you ever discover the exact sequence of events/conditions that caused this failure, let us know; anything we can do to prevent (or at least warn about) potential failure modes would be a great addition to the docs.

[damascene]

I'm having the exact same error, It might get solved if I reinstall docker and go from start but apparently there is an issue there on Ubuntu 20.04 Edit: Can't confirm it 100% but seems like running briefcase create solved the issue without removing docker using docker system prune -a