Fix #1273 by correcting interpolation
Fix #1273 by correcting interpolation

Don’t ask me why it works, but it does:

>>> import regex
>>> print(regex.sub(r'([\]*`])', r'\\\1', 'a ** b ] `c`'))
a \*\* b \] \`c\`
Charcoal-SE/SmokeDetector,Charcoal-SE/SmokeDetector