generate package.xml

[asmodehn]

We need a way to generate package.xml file, and avoid discrepancies between python package details and catkin package details...

[asmodehn]

This is linked with the fact that we do NOT want to build install space (because of python intricacies when deploying installing packages).

The idea for the catkin_pip workflow is :

1. work in devel space with catkin_pip and other ros components
2. release the catkin_pip project as a pip package in pypi
3. make install only generate an empty ros package, with dependency to the pip package (no other pippackage) + any required ros packages dependencies => package.xml needs to be crafted.
4. That package could be release among ros packages, but would install just a package.xml to help rosdep satisfy dependencies and retrieve it s python code from pypi.

This should work fine as long as everyone uses rosdep for dependencies, and rosdep support pip (which I think it does).

[asmodehn]

We should be careful to not break what already works though, and we should probably add this new package build as an extra feature : catkin_symbolic_package() building a deb package that just reference another package in another rosdep supported package manager.

[asmodehn]

Not sure if this is really useful or not after all.
We still need to test the thirdparty package scenario, but if having it in the release repo only is working, then generating it is not really needed (and might be dropped, given the complexity of this).

In any case, the documentation in that package can refer tothe original package documentation.
Ref : http://wiki.ros.org/rosdoc_lite#Linking_to_External_Third_Party_Documentation

[asmodehn]

This is still useful in case we want to use a python repository, in a catkin_pip environment => we do not need to store the package.xml in the repository to test our "development" (pure) python package with ROS.

So one would need only a CMakeLists.txt to get the pure python package to build with catkin_pip.

The release repo can set his own package.xml as with thirdparty release afterwards anyway regardless.

This is because currently, even using catkin_pip, catkin_package complains if there is no package.xml in the source repo:

CMake Error: File /home/alexv/Projects/catkin_ws/src/pyzmp/package.xml does not exist.
CMake Error at /opt/ros/indigo/share/catkin/cmake/stamp.cmake:10 (configure_file):
  configure_file Problem configuring file
Call Stack (most recent call first):
  /opt/ros/indigo/share/catkin/cmake/catkin_package_xml.cmake:61 (stamp)
  /opt/ros/indigo/share/catkin/cmake/catkin_package_xml.cmake:39 (_catkin_package_xml)
  /opt/ros/indigo/share/catkin/cmake/catkin_package.cmake:95 (catkin_package_xml)
  CMakeLists.txt:15 (catkin_package)


CMake Error at /opt/ros/indigo/share/catkin/cmake/catkin_package.cmake:112 (message):
  catkin_package() 'catkin' must be listed as a buildtool dependency in the
  package.xml
Call Stack (most recent call first):
  /opt/ros/indigo/share/catkin/cmake/catkin_package.cmake:98 (_catkin_package)
  CMakeLists.txt:15 (catkin_package)

[asmodehn]

Already implemented there : https://github.com/mikepurvis/catkin_tools_python

Not sure how to integrate yet. delayed, not for release 0.2.