tests: escape backslash in makepatch.py inline file
This avoids some SyntaxWarning on Python 3.8 due to unescaped \.
Differential Revision: https://phab.mercurial-scm.org/D5840
tests: use raw strings in test-cbor.py
To avoid SyntaxWarning on Python 3.8 due to invalid \ escape.
Differential Revision: https://phab.mercurial-scm.org/D5839