Make PySVN optional for unit tests.
The unit tests no longer depend on PySVN. Some of the remaining tests

using Subversion repositories have been updated to use Git instead, and

the rest now use a new TestTool that is based off Git but has many

testable properties for things like branches, commits, basedir, etc.
You can now remove PySVN from your system and run the test suite. The

real Subversion-specific tests will just skip, and all main tests will

run.

Removed PySVN temporarily from the system and ran the test suite. All

tests passed (except the SVN tests, which skipped).
Added it back and all tests passed.