Drop support for Python versions 2.7 and 3.4

[biozz]

As discussed in #1124, we can start the process of dropping older python versions support.

Main changes are driven by following this article and include:

• remove py3compat module
• remove try/except imports which were necessary for Python 2
• remove six imports and usage
• cleanup setup.py
• cleanup tox.ini

Other changes include:

• remove Python 2 related import of ConfigParser and urlparse in circus/util.py
• change to lambda sorting in circus/config.py
• add Loader=yaml.FullLoader in yaml.load calls
• add IS_WINDOWS skips for couple of tests
• add __pycache__ removal in make clean command
• remove coding line, because of PEP 3120

I also did a small test on Windows (inside VirtualBox), thats why there are couple of skipIf(IS_WINDOWS) in the changes. Unfortunately the tests are completely broken in Windows and I think proper fixing should be done separately.

Finally, I went through examples directory and tried starting several of those to make sure the changes didn't break anything.

[coveralls]

Coverage increased (+0.9%) to 63.911% when pulling 48dadba3deb78778806565bb52b30501032fc58d on biozz:drop-py27-py34 into bfa21890605462f34ff59c20b2a3e1d11bfa4704 on circus-tent:master.

[coveralls]

Coverage remained the same at ?% when pulling 8e128e73d2e960a5f422ca183fef10c6578debf4 on biozz:drop-py27-py34 into 422d64dbf5823bd5c81c08d0b2a881c296b3d603 on circus-tent:master.

[huydangg]

I am facing the problem when I set httpd is True.

Traceback (most recent call last): File "", line 1, in File "/data1/python38/lib/python3.8/site-packages/circusweb/circushttpd.py", line 17, in from circusweb.util import AutoDiscovery, run_command File "/data1/python38/lib/python3.8/site-packages/circusweb/util.py", line 12, in from circusweb.session import get_controller File "/data1/python38/lib/python3.8/site-packages/circusweb/session.py", line 1, in from circusweb.controller import Controller File "/data1/python38/lib/python3.8/site-packages/circusweb/controller.py", line 2, in from circusweb.client import AsynchronousCircusClient File "/data1/python38/lib/python3.8/site-packages/circusweb/client.py", line 9, in from circus.py3compat import string_types ModuleNotFoundError: No module named 'circus.py3compat'`

This is relate to "remove py3compat module"?

Thanks.

[biozz]

Yes, you are right. I completely forgot about circus-web, sorry. I will try to have a look at it as soon as possible. Thank you for reporting!

[biozz]

@huydangg I had a look on this issue and fixing this import is just the tip of the iceberg... We will have to make circus-web compatible with python3 as well as with the new versions of tornado. I will try to make it happen, but it is not trivial and might take quite some time. For now you can try using previous versions of circus/circus-web/tornado.

[huydangg]

@biozz Thank you for your support. I will try using previous version.