Deprecation warning due to invalid escape sequences

[tirkarthi]

Describe the bug

Deprecation warnings are raised due to invalid escape sequences. This can be fixed by using raw strings or escaping the literals. pyupgrade also helps in automatic conversion : https://github.com/asottile/pyupgrade/

To Reproduce

find . -iname '*.py' | grep -v example | xargs -P4 -I{} python3.8 -Wall -m py_compile {}
./tools/c7n_sentry/test_sentry.py:50: DeprecationWarning: invalid escape sequence \m
  msg2 = """
./tests/zpill.py:274: DeprecationWarning: invalid escape sequence \d
  response_data = re.sub("\d{12}", ACCOUNT_ID, response_data)  # noqa

Background (please complete the following information):

• OS: [e.g. OSX 10.15]
• Python Version: 3.8
• Custodian Version: master branch
• Tool Version: [if applicable]
• Cloud Provider: [e.g. gcp, aws, azure]
• Policy: [please exclude any account/sensitive information]