Fixes: Issue 12: Fix tests to work on OS X.
Fixes:
Issue 12: Fix tests to work on OS X.

davidlbaird/pyfakefs,google-code-export/pyfakefs,tectronics/pyfakefs,tomviner/pyfakefs,jmcgeheeiv/pyfakefs,mrbean-bremen/pyfakefs,dougluce/pyfakefs,danieldc/pyfakefs,chromy/pyfakefs,sri85/pyfakefs,pytest-dev/pyfakefs,mrbean-bremen/pyfakefs