Deprecation warning due to invalid escape sequences

[tirkarthi]

Deprecation warning due to invalid escape sequences. Using raw strings or escaping them again helps in resolving this. Check https://github.com/asottile/pyupgrade/ for automatic fix of this.

find . -iname '*.py' | grep -Ev 'setup|rdf4|tool' | xargs -P4 -I{} python3.8 -Wall -m py_compile {}
./tests.py:65: DeprecationWarning: invalid escape sequence \$
  env = parse_dotenv('FOO="foo\${BAR}"')