Gracefully handle missing pytest-xdist distribution.
Hard failure instead of graceful, from feedback provided by vitaly
Merge remote-tracking branch 'upstream/master' into graceful-missing-pytest-xdist
Vector: add undocumented but required self.encoders field
Merge branch 'vector' into utility-encoder
Vector: add undocumented but required self.encoders field
add imports for Vector*Encoder
add imports to MultiEncoder
add PassThru to init
Merge branch 'vector' into utility-encoder
Vector fix encode len check
Merge pull request #442 from oxtopus/graceful-missing-pytest-xdist

Detect missing pytest-xdist module
Merge branch 'master' into utility-encoder
UtilityEncodere: move to encoders/extras