A while back we had made changes to the hosting services to require

keyword arguments for check_repository. In the Assembla

implementation, this change ended up changing the assembla_project_id

field to not include a default value. This field is required when using

a Perforce repository, but is not when using SVN.
In practice, the repository form will always provide this, but we had a

unit test that didn't. To prefer existing compatibility, I've given this

field a None default again, and raise a ValueError if it's not

provided in the Perforce case.
While in here I also noticed that the skip messages for unit tests with

SVN repositories were wrong.

Ran unit tests.