catkin_prepare_release should validate metapackages

[wjwwood]

Specifically that they have valid CMakeLists.txt. A lot of people are going to run into this problem while releasing with bloom. It would be nice to have this tool check.

It could output:

cat <<EOF
Metapackage <metapackage_name> does not have a valid CMakeLists.txt, therefore it does not conform to REP-0127, see: http://ros.org/reps/rep-0127.html#metapackage

The CMakeLists.txt should look like this:
<CMakeLists.txt that was expected>
EOF

Instead of its normal command output, which would be safe for people doing something like this:

`catkin_prepare_release`

[wjwwood]

It should also check that the package.xml has a <buildtool_depend> on catkin.

[wjwwood]

@dirk-thomas and @tfoote for review

[wjwwood]

Error output looks something like this:

Invalid metapackage at path '/Users/william/devel/catkin_pkg/test/data/metapackages/no_cmake':
  Metapackage 'no_cmake': No CMakeLists.txt

See requirements for metapackages: http://ros.org/reps/rep-0127.html#metapackage

Or

WARNING: Metapackage "invalid_depends" should not have other dependencies besides a buildtool_depend on catkin and run_depends.
Invalid metapackage at path '/Users/william/devel/catkin_pkg/test/data/metapackages/invalid_depends':
  Metapackage 'invalid_depends': Has build, buildtool, and/or test depends, but only run depends are allowed (except buildtool catkin)

See requirements for metapackages: http://ros.org/reps/rep-0127.html#metapackage

The extra WARNING: ... line is coming from find_packages which checks a few things about metapackages.

[tfoote]

+1

[dirk-thomas]

Should these error message be printed to , file=sys.stderr?

[wjwwood]

@dirk-thomas updated for review again.

[dirk-thomas]

+1

[wjwwood]

I will wait to merge this until ros-infrastructure/catkin_pkg#40 is merged and catkin_pkg 0.1.11 is released.