matplotlib Code

update known good baselines using freetype 2.3.5

make the buildbot point to devbb

buildbot: prevent DirectoryUpload failure when all tests pass

updated baseline empty datetime

fix formatter4 unit test and image

removed known failure decorator for sf bug 2846058

buildbot: delete build directory when re-building

New version of empty_datetime.png; it is not clear what caused the change,
but the new version is nicer, so let's hope it is produced consistently now.
The difference is that there is no x ticklabel on the far left.

testing: add support for KnownFailures

buildbot: wipe build directory to ensure clean rebuilds