Default NetCDF dimensionless unit.
Fix string formatting bugs in STASH object error messages.
Add pp constraint conversion test where STASH=stash-object (instead of string).
Allow STASH-constraint conversion where reference is a STASH object (instead of a string).
Allow users to choose the number of processors used for running tests.
Merge pull request #1306 from pp-mo/pp_stash_constrain

Pp stash constrain
Move _messages_from_filename to _GribMessage.
On-demand value lookup.
Merge pull request #1320 from SciTools/v1.7.x

Merge from 1.7
Extended GRIB2 shape of the earth coverage.
Merge pull request #1321 from bjlittle/grib_shape_of_earth_0

Extended GRIB2 shape of the earth coverage.
Review tweaks
Merge pull request #1318 from rhattersley/lazy-grib

Lazy evaluation of GRIB keys
Lazy data.
Review fixes.
Factor out test message creation.
Deprecate `auto_regularise`.
Merge pull request #1315 from ajdawson/testing-processors

Allow users to choose the number of processors used for running tests.
Minor review actions.
Data -> Message