Fix Arch Linux rosdep mappings.

Cf. #2891
Merge pull request #2891 from bchretien/master

Fix Arch Linux rosdep mappings.
Merge pull request #3101 from shadow-robot/master

Add source sections to these 3 packages to allow the pre-release test
rosconsole_bridge: 0.3.3-0 in 'indigo/distribution.yaml' [bloom]
add doc/source for rosconsole_bridge
Merge pull request #3102 from dirk-thomas/bloom-rosconsole_bridge-0

rosconsole_bridge: 0.3.3-0 in 'indigo/distribution.yaml' [bloom]
rosdep: integrated gentoo into base and python

Fixes #1036
Merge pull request #3103 from ros/gentoo_cleanup

rosdep: integrated gentoo into base and python
We have to keep the empty file...

Fixes #3104
Update 20-default.list
gentoo: it has to have an empty yaml dict
add special handling for rosdep files which are {}
shadow_robot: 1.3.0-0 in 'hydro/distribution.yaml' [bloom]
sr_config: 1.3.0-0 in 'hydro/distribution.yaml' [bloom]
Merge pull request #3105 from ros/fix_travis_for_empty_rosdep

add special handling for rosdep files which are {}
Merge pull request #3106 from toliver/bloom-shadow_robot-0

shadow_robot: 1.3.0-0 in 'hydro/distribution.yaml' [bloom]
Merge pull request #3107 from toliver/bloom-sr_config-0

sr_config: 1.3.0-0 in 'hydro/distribution.yaml' [bloom]
add python-pygraphviz for trusty
geometry_experimental: 0.5.0-0 in 'indigo/distribution.yaml' [bloom]
add source and doc