FindResourcePath("drake/examples/...") does not work in drake-shambhala

[EricCousineau-TRI]

I tried adding a downstream find_resource Python test in Drake Shambhala, but the resource path for atlas_convex_hull.urdf is broken:
RobotLocomotion/drake-external-examples#85

Presently, //examples data files are installed to ${drake_install}/share/drake/examples, but the resource path is implicitly defined as ${drake_install}/share/drake (and I believe it remains this even if I try to append ${drake_install}/share to the search paths).

Because drake/ is appended to the search path, I cannot do FindResourcePath("examples/...") because it requires that paths start with drake.

If I have drake::(anonymous namespace)::FileExists print out the path, my ctest output looks like this:

$ ctest -V -R test_find_resource_py
...
1: Test command: /usr/bin/python2.7 "${drake_shambhala}/drake_cmake_installed/src/find_resource/test_find_resource.py"
1: Environment variables: 
1:  PYTHONPATH=${drake_install}/lib/python2.7/site-packages:${orig_pythonpath}
1: Test timeout computed to be: 1500
1: file path: ${drake_install}/lib/python2.7/site-packages/pydrake/../../../../share/drake/drake/examples/atlas/urdf/atlas_convex_hull.urdf
1: Currently not working
1: Error: could not find resource: drake/examples/atlas/urdf/atlas_convex_hull.urdf
1/1 Test #1: test_find_resource_py ............   Passed    0.21 sec

The file ${drake_install}/lib/python2.7/site-packages/pydrake/../../../../share/drake/examples/atlas/urdf/atlas_convex_hull.urdf does exist.

While the fix seems simple (install "examples" to ${drake_install}/share/drake/drake/examples}), debugging this was rather confusing, and it'd be nice this logic were simplified to avoid this confusion in the future.

@fbudin69500 or @jwnimmer-tri, may I ask if either of you could weigh in on this?
(I can make the change if you like.)

[jwnimmer-tri]

Maybe #7774 is what you're getting at?

[EricCousineau-TRI]

Yup, seems so!
Would this simplify the logic in find_resource.cc?

[EricCousineau-TRI]

Will move my questions to #7774.