Build fails: Architecture: all, no ‘python3-dev’, but ‘setup.py’ expects it

[Ben Finney <ben+debian@benfinney.id.au>]

Howdy all,

I am experiencing a build failure on a Python 3 package [0].

The package has “Architecture: all”, and should not need any
architecture-specific build tools. The package builds no Python
extensions.

I assume (and Lintian agrees) that such a package should not have
“Build-Depends: python3-dev”.

Yet when I try to build the package using a clean up-to-date Sid chroot,
it fails:

=====
dh binary --with bash-completion,python3 --buildsystem=pybuild
   dh_testroot -O--buildsystem=pybuild
   dh_prep -O--buildsystem=pybuild
   dh_auto_install -O--buildsystem=pybuild
I: pybuild base:184: /usr/bin/python3 setup.py install --root /build/xkcdpass-1.6.3/debian/xkcdpass
running install
error: invalid Python installation: unable to open /usr/lib/python3.5/config-3.5m-x86_64-linux-gnu/Makefile (No such file or directory)
E: pybuild pybuild:274: install: plugin distutils failed with: exit code=1: /usr/bin/python3 setup.py install --root /build/xkcdpass-1.6.3/debian/xkcdpass
dh_auto_install: pybuild --install -i python{version} -p 3.5 --dest-dir /build/xkcdpass-1.6.3/debian/xkcdpass returned exit code 13
debian/rules:35: recipe for target 'binary' failed
make: *** [binary] Error 25
dpkg-buildpackage: error: fakeroot debian/rules binary gave error exit status 2
=====

Why is that architecture-specific build tool being specified for an
“Architecture: all” build system?

When I amend the package and specify “Build-Depends: python3-dev”, the
build succeeds but Lintian (correctly) reports
“build-depends-on-python-dev-with-no-arch-any”.

What is broken here? How can I find out?


[0] ‘xkcdpass’, I am packaging upstream version “1.6.3”.

-- 
 \       “Faith is the determination to remain ignorant in the face of |
  `\                 all evidence that you are ignorant.” —Shaun Mason |
_o__)                                                                  |
Ben Finney