docbuild.py fails for packages which are in root of git repository

[mikeferguson]

Currently failing trying to build graft:

Retrieve the ROS build environment by sourcing /opt/ros/hydro/setup.bash
Considering /tmp/graft_hydro_docbuild/src/src/package.xml
Considering /tmp/graft_hydro_docbuild/src/test_attitude.launch/package.xml
Considering /tmp/graft_hydro_docbuild/src/include/package.xml
Considering /tmp/graft_hydro_docbuild/src/.git/package.xml
Considering /tmp/graft_hydro_docbuild/src/CMakeLists.txt/package.xml
Considering /tmp/graft_hydro_docbuild/src/msg/package.xml
Considering /tmp/graft_hydro_docbuild/src/package.xml/package.xml
Considering /tmp/graft_hydro_docbuild/src/test_absolute.launch/package.xml
Considering /tmp/graft_hydro_docbuild/src/config/package.xml
Considering /tmp/graft_hydro_docbuild/src/README.md/package.xml
Considering /tmp/graft_hydro_docbuild/src/test_graft.launch/package.xml
Generating docs for: 
Executing command "chmod -R 777 /tmp/graft_hydro_docbuild/docs"
chmod: cannot access `/tmp/graft_hydro_docbuild/docs': No such file or directory
/!\ Failed to execute command "['chmod', '-R', '777', '/tmp/graft_hydro_docbuild/docs']" with return code 1
Traceback (most recent call last):
  File "/runscript", line 91, in <module>
    run_docbuild(sys.argv[1], sys.argv[2])
  File "/runscript", line 43, in run_docbuild
    call(['chmod', '-R', '777', os.path.join(workspace, 'docs')])
  File "/runscript", line 60, in call
    raise BuildException(msg)
__main__.BuildException