catkin_lint not compatible with Python 2 anymore

[rhaschke]

Latest PyPi release of catkin_lint is not compatible with Python 2.7 anymore:

  Traceback (most recent call last):
    File "/usr/local/bin/catkin_lint", line 52, in <module>
      from catkin_lint.main import main
    File "/usr/local/lib/python2.7/dist-packages/catkin_lint/__init__.py", line 39, in <module>
      from ._version import version as __version__
    File "/usr/local/lib/python2.7/dist-packages/catkin_lint/_version.py", line 10
      version: str
             ^
  SyntaxError: invalid syntax

It would be great if a version compatible with Python 2 would still be available via pip install.

[rhaschke]

Looks like the Python 3 requirement comes from (a new release of) setuptools-scm, which generates _version.py.
Adding a python_requires=">=3" in setup(...) should resolve the issue.
industrial_ci pinned the version manually for now.