gnuradio 3.7.10.1 build needs docbook environment variable

[X] Confirmed this is a problem with only one, specific formula and not Homebrew/brew? If it's a general Homebrew/brew problem please file this issue at https://github.com/Homebrew/brew/issues/new
[X] Ran brew update and retried your prior step?
[X] Ran brew doctor, fixed as many issues as possible and retried your prior step?
What you were trying to do (and why): I wanted to upgrade to gnuradio 3.7.10.1 by building it from source but the update kept failing for a while.

What happened (include command output) The build fails at about 13% with the following error (only relevant part of build log including a bit of context):

[ 13%] Generating viterbi_combined_sb.h, viterbi_combined_ss.h, viterbi_combined_si.h, viterbi_combined_ib.h, viterbi_combined_is.h, viterbi_combined_ii.h, viterbi_combined_fb.h, viterbi_combined_fs.h, viterbi_combined_fi.h, viterbi_combined_cb.h, viterbi_combined_cs.h, viterbi_combined_ci.h
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f gr-trellis/python/trellis/CMakeFiles/pygen_gr_trellis_python_trellis_3ce01.dir/build.make gr-trellis/python/trellis/CMakeFiles/pygen_gr_trellis_python_trellis_3ce01.dir/depend
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis && /usr/local/bin/python2 -B /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis/generate_helper.py viterbi_combined_XX viterbi_combined_XX.h.t sb ss si ib is ii fb fs fi cb cs ci
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build && /usr/local/Cellar/cmake/3.7.2/bin/cmake -E cmake_depends "Unix Makefiles" /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1 /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/python/trellis /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis/CMakeFiles/pygen_gr_trellis_python_trellis_3ce01.dir/DependInfo.cmake --color=
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f gr-trellis/examples/python/CMakeFiles/pygen_gr_trellis_examples_python_68c3e.dir/build.make gr-trellis/examples/python/CMakeFiles/pygen_gr_trellis_examples_python_68c3e.dir/depend
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build && /usr/local/Cellar/cmake/3.7.2/bin/cmake -E cmake_depends "Unix Makefiles" /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1 /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/examples/python /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/examples/python /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/examples/python/CMakeFiles/pygen_gr_trellis_examples_python_68c3e.dir/DependInfo.cmake --color=
Scanning dependencies of target pygen_gr_trellis_python_trellis_3ce01
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f gr-trellis/python/trellis/CMakeFiles/pygen_gr_trellis_python_trellis_3ce01.dir/build.make gr-trellis/python/trellis/CMakeFiles/pygen_gr_trellis_python_trellis_3ce01.dir/build
xmlto: /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/doc/gr-trellis.xml does not validate (status 3)
xmlto: Fix document syntax or use --skip-validation option
[ 13%] Generating sccc_decoder_b.h, sccc_decoder_s.h, sccc_decoder_i.h
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis && /usr/local/bin/python2 -B /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis/generate_helper.py sccc_decoder_X sccc_decoder_X.h.t b s i
/tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/doc/gr-trellis.xml:6: warning: failed to load external entity "/tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/doc/docbookx.dtd"
]>
^
warning: failed to load external entity "/tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/doc/docbookx.dtd"
validity error : Could not load the external subset "docbookx.dtd"
Document /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/doc/gr-trellis.xml does not validate
Scanning dependencies of target pygen_gr_trellis_examples_python_68c3e
make[2]: *** [gr-trellis/doc/gr-trellis.html] Error 13
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f gr-trellis/examples/python/CMakeFiles/pygen_gr_trellis_examples_python_68c3e.dir/build.make gr-trellis/examples/python/CMakeFiles/pygen_gr_trellis_examples_python_68c3e.dir/build
make[1]: *** [gr-trellis/doc/CMakeFiles/gr_trellis_html.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 13%] Generating __init__.pyc, fsm_utils.pyc
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis && /usr/local/bin/python2 /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/python_compile_helper.py /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/python/trellis/__init__.py /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/python/trellis/fsm_utils.py /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis/__init__.pyc /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis/fsm_utils.pyc
[ 13%] Generating __init__.pyo, fsm_utils.pyo
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis && /usr/local/bin/python2 -O /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/python_compile_helper.py /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/python/trellis/__init__.py /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/python/trellis/fsm_utils.py /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis/__init__.pyo /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/python/trellis/fsm_utils.pyo
[ 13%] Shebangin test_tcm.py
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/examples/python && /usr/local/bin/python2 -c "import re; R=re.compile('^#!.*\$\\n',flags=re.MULTILINE); open('/tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/examples/python/test_tcm.py.exe','w').write('#!/usr/local/bin/python2\\n'+R.sub('',open('/tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/examples/python/test_tcm.py','r').read()))"
[ 13%] Shebangin test_cpm.py
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/examples/python && /usr/local/bin/python2 -c "import re; R=re.compile('^#!.*\$\\n',flags=re.MULTILINE); open('/tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/examples/python/test_cpm.py.exe','w').write('#!/usr/local/bin/python2\\n'+R.sub('',open('/tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/gr-trellis/examples/python/test_cpm.py','r').read()))"
[ 13%] Generating sccc_decoder_combined_fb.h, sccc_decoder_combined_fs.h, sccc_decoder_combined_fi.h, sccc_decoder_combined_cb.h, sccc_decoder_combined_cs.h, sccc_decoder_combined_ci.h
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis && /usr/local/bin/python2 -B /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis/generate_helper.py sccc_decoder_combined_XX sccc_decoder_combined_XX.h.t fb fs fi cb cs ci
[ 13%] Generating pccc_decoder_b.h, pccc_decoder_s.h, pccc_decoder_i.h
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis && /usr/local/bin/python2 -B /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis/generate_helper.py pccc_decoder_X pccc_decoder_X.h.t b s i
[ 13%] Generating pccc_decoder_combined_fb.h, pccc_decoder_combined_fs.h, pccc_decoder_combined_fi.h, pccc_decoder_combined_cb.h, pccc_decoder_combined_cs.h, pccc_decoder_combined_ci.h
cd /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis && /usr/local/bin/python2 -B /tmp/gnuradio-20170407-80087-5mbo3x/gnuradio-3.7.10.1/build/gr-trellis/include/gnuradio/trellis/generate_helper.py pccc_decoder_combined_XX pccc_decoder_combined_XX.h.t fb fs fi cb cs ci
[ 13%] Built target pygen_gr_trellis_examples_python_68c3e
[ 13%] Built target pygen_gr_trellis_python_trellis_3ce01
[ 13%] Built target trellis_generated_includes
[ 13%] Built target volk_obj
make: *** [all] Error 2

What you expected to happen No error while building.
Possible fix: By looking at the error validity error : Could not load the external subset "docbookx.dtd" from the included log it was likely the error had something to do with docbook, so I reinstalled it and noticed the caveats:

To use the DocBook package in your XML toolchain, you need to add the following to your ~/.bashrc:

export XML_CATALOG_FILES="/usr/local/etc/xml/catalog"

Therefore I set the environment variable as suggested prior to building and the building succeeded.

Edit: Full log of another build with same error: https://gist.github.com/muellermartin/fee1391b48e59bb4c12088ec44bd4619#file-05-make

Homebrew / homebrew-core

gnuradio 3.7.10.1 build needs docbook environment variable #12163