This is the promised second step on single-quoted strings. These had
existed because our source transformer didn't turn r'' into b'', so we
had tagged some strings as r-strings to get "native" strings on both
Pythons. Now that the transformer is gone, we can dispense with this
hg locate 'set:added() or modified() or clean()' | egrep '.*\.py$' | xargs egrep --color=never -n -- \[\^b\]\[\^a-z\]r\'\[\^\'\\\\\]\*\'\[\^\'\
in an emacs grep-mode buffer, and then used a keyboard macro to
iterate over the results and remove the r prefix as needed.
- skip-blame removing unneeded r prefixes left over from Python 3 migration.