Fix hacking tests on osx

There were a few incompatibilities with the hacking tests and
OSX. Readlink -f doesn't work so use cd and pwd instead. Importing
a module with path separators doesn't work, so recursively import
the module. Finally the extra / in the find command was not needed.

Add a 'set -e' to run_pep8 to make sure test fails on any error

Ignore paste as it doesn't have an __init__ in its top level directory

Change-Id: Ifc66da7b872faa08f3be98f8b10486181ba77861
Merge "Fix hacking tests on osx"