Weird FTBFS for dephell_markers somewhere in setuptools … egg_base is blank?

Originally I filed this as https://github.com/dephell/dephell_markers/issues/6, but I think it is something wrong with setuptools in the end.

[   31s] + /usr/bin/python3 setup.py install -O1 --skip-build --force --root /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64 --prefix /usr
[   31s] running install
[   31s] running install_lib
[   31s] creating /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr
[   31s] creating /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib
[   31s] creating /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7
[   31s] creating /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages
[   31s] creating /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers
[   31s] copying build/lib/dephell_markers/_cached_property.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers
[   31s] copying build/lib/dephell_markers/_constants.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers
[   31s] copying build/lib/dephell_markers/__init__.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers
[   31s] copying build/lib/dephell_markers/_markers.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers
[   31s] creating /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker
[   31s] copying build/lib/dephell_markers/_marker/_version.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker
[   31s] copying build/lib/dephell_markers/_marker/_base.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker
[   31s] copying build/lib/dephell_markers/_marker/__init__.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker
[   31s] copying build/lib/dephell_markers/_marker/_string.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker
[   31s] creating /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation
[   31s] copying build/lib/dephell_markers/_operation/_or.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation
[   31s] copying build/lib/dephell_markers/_operation/_base.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation
[   31s] copying build/lib/dephell_markers/_operation/__init__.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation
[   31s] copying build/lib/dephell_markers/_operation/_and.py -> /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/__init__.py to __init__.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_cached_property.py to _cached_property.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_constants.py to _constants.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker/__init__.py to __init__.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker/_base.py to _base.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker/_string.py to _string.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_marker/_version.py to _version.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_markers.py to _markers.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation/__init__.py to __init__.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation/_and.py to _and.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation/_base.py to _base.cpython-37.pyc
[   31s] byte-compiling /home/abuild/rpmbuild/BUILDROOT/python-dephell-markers-1.0.2-0.x86_64/usr/lib/python3.7/site-packages/dephell_markers/_operation/_or.py to _or.cpython-37.pyc
[   31s] writing byte-compilation script '/tmp/tmpc71pyy4r.py'
[   31s] /usr/bin/python3 /tmp/tmpc71pyy4r.py
[   31s] removing /tmp/tmpc71pyy4r.py
[   31s] running install_egg_info
[   31s] error: error in 'egg_base' option: '' does not exist or is not a directory
[   31s] error: Bad exit status from /var/tmp/rpm-tmp.mNcdbA (%install)
[   31s] 
[   31s] 
[   31s] RPM build errors:
[   31s]     Bad exit status from /var/tmp/rpm-tmp.mNcdbA (%install)
[   31s] 
[   31s] stitny failed "build python-dephell-markers.spec" at Mon Dec  2 09:52:22 UTC 2019.
[   31s]

Completely build log with all details

My attempt to debug the issue in pdb

Reproduce the logged python3 setup.py install command and inspect setuptools' install_egg_info handling of the blank egg_base option. Start with the provided build log and pdb debugging gist, then trace the failing entry point. Done means the reported build completes without the egg_base directory error and the cause is covered by a regression test.