Fix requirements_style_check on BSD platforms

On Linux, the sort command implicitly ignore non-alphanumeric characters
when sorting.  Since the '>' character has an ASCII value greater than
the '-' character, the following list will be sorted on Linux, but not
on a Mac:

SQLAlchemy>=0.7.8,<=0.9.99
sqlalchemy-migrate>=0.9.1

This makes sort explicitly ignore such characters and will keep the
tests consistent across different environments.

Closes-Bug: #1324945
Change-Id: I559ae4b4c3e2a7d190af9d4b1517dfaf23d114b1
Merge "Fix requirements_style_check on BSD platforms"