Travis CI failing

[stwirth]

Since #93 got merged, it seems that Travis CI is failing with

======================================================================
ERROR: Failure: ImportError (No module named pycodestyle)
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Traceback (most recent call last):
  File "/home/travis/virtualenv/python2.7.17/lib/python2.7/site-packages/nose/loader.py", line 418, in loadTestsFromName
    addr.filename, addr.module)
  File "/home/travis/virtualenv/python2.7.17/lib/python2.7/site-packages/nose/importer.py", line 47, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/home/travis/virtualenv/python2.7.17/lib/python2.7/site-packages/nose/importer.py", line 94, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/tmp/capabilities_build/src/capabilities/test/unit/test_code_quality.py", line 1, in <module>
    import pycodestyle
ImportError: No module named pycodestyle

e.g. https://travis-ci.org/github/osrf/capabilities/builds/681663229

The package.xml defines a rosdep on python-pycodestyle:

capabilities/package.xml

Lines 44 to 45 in df54fa8

	<test_depend condition="$ROS_PYTHON_VERSION == 2">python-pycodestyle</test_depend>
	<test_depend condition="$ROS_PYTHON_VERSION == 3">python3-pycodestyle</test_depend>

.travis.yml installs other python rosdeps via pip but not pycodestyle:

capabilities/.travis.yml

Lines 6 to 14 in df54fa8

	install:
	- pip install nose coverage pep8 PyYAML catkin_pkg rospkg empy python-coveralls
	- sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu bionic main" > /etc/apt/sources.list.d/ros-latest.list'
	- wget http://packages.ros.org/ros.key -O - | sudo apt-key add -
	- sudo apt-get update
	- sudo apt-get install python-rosdep
	- sudo `which rosdep` init
	- rosdep update
	- rosdep install --from-paths ./ --rosdistro melodic -y

I think python-pycodestyle might not be installed automatically during the rosdep install because ROS_PYTHON_VERSION is not set yet at this point.

Solution A: Add pycodestyle to line 7 in travis.yml

Solution B: Set ROS_PYTHON_VERSION=2 before line 14 in travis.yml (and cleanup line 7: remove the packages that are installed via rosdep)

If B works I think it would be the better solution.