Fix Missing Imports

This change fixes a missing import that came up with I created a buildbot instance for testing OSX and Windows (which is coming soon...):

https://build.pyfarm.net/builders/master-postgres-mac-2.7/builds/8/steps/run%20tests/logs/stdio

This came up because we're receiving a BAD_REQUEST response on OS X which is not something we're getting on Linux and the BAD_REQUEST object itself is not being imported. 

https://build.pyfarm.net/builders/master-postgres-mac-2.7/builds/9/steps/run%20tests/logs/stdio

The change fixes the missing import but unfortunately the test is still failing on OS X for the moment.