Throw an error in FieldTracker when using untracked field with .previous #324
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Problem
Previously if
previous
was called on a field tracker and the field was not being tracked it would returnNone
. Having consistent behavior betweenprevious
andhas_changed
would seem to make sense, but there may be a reason why this is not so?Solution
I've moved the
FieldError
exception intoprevious
fromhas_changed
;has_changed
callesprevious
so the exception will still be used fromhas_changed
.Commandments
CHANGES.rst
file to describe the changes, and quote according issue withGH-<issue_number>
.I can add a test for this if you think it's worth merging?