python3-colcon colcon build reports an error on Ubuntu Xenial

[paulbovbel]

colcon build on an ubuntu:xenial container reports the following error:

ERROR:colcon.colcon_core.entry_point:Exception loading extension 'colcon_core.package_identification.python': No module named 'setuptools.config'

It looks like the system packaged setuptools doesn't include this module in xenial - this can be worked around by upgrading the system setuptools using sudo python3 -m pip install setuptools -U.

[dirk-thomas]

Can you clarify which instructions you followed for building the package. The documentation mentions that updating setuptools might be necessary.

[paulbovbel]

Apologies - this occurs when having installed python3-colcon-common-extensions from repo.ros2.org on a fresh ubuntu xenial container.

[sloretz]

It looks like setuptools.config was added in 30.3.0. Would changing the install_requires for setuptools to setuptools >= 30.3.0 cause it to be upgraded when colcon-core is installed via pip?

[dirk-thomas]

For Debian packages there is no way for the colcon Debian package to fix the problem / install the newer setuptools version automatically. But #91 ensures for pip installed packages that the dependency is new enough as well as prints a better error message in the Debian case where the dependency is too old.