I might be missing something, but I feel like this whole file should be in fixtures/setup_api_listener, or split into behavior in a utils/ module with a fixture wrapper in fixtures/. tests/common/ appears to be created by this commit.

The bottle listener should probably be running as something like a multiprocessing.Process object[1]. This would do a few helpful things:
- The fixture could benefit from using pytest's builtin-in tmpdir fixture, obviating the need to clean up the file
- The location of the script to start the listener doesn't have to be derived by the setup_api_listener fixture, it only has to be imported by it and used like any other python object.

[1]http://docs.python.org/2/library/multiprocessing.html#multiprocessing.Process