manifest: call m1.load and m2.load before writing a subtree As part of refactoring the manifest, certain test cases started failing because writesubtrees was called with p1 and p2 manifests that had not been loaded (so accessing m1._dirs resulted in an empty set). Let's call _load on these before attempting to access _dirs. This was caught by tests when future patches were applied.

histedit: correct output of error when 'base' is from the edit list This was made more obvious by marmoute's recent rearrangement of this code.

py3: split check of pygments-using files from the rest of the tree If we don't do this, people without pygments installed in their Python 3 environment silently stop checking test-check-py3-compat, which isn't really what we wanted. This preserves stability of the test output while still letting anyone with a recent-enough Python 3 run the majority of the Python 3 compat checking test.