Resolve invalid escape sequence
Resolve invalid escape sequence

When run not as a decorator dynamodb2 displays an invalid escape sequence error
/moto/dynamodb2/responses.py:603: DeprecationWarning: invalid escape sequence \s
  '\s*([=\+-])\s*', '\\1', update_expression)
spulec/moto,spulec/moto,william-richard/moto,spulec/moto,spulec/moto,william-richard/moto,william-richard/moto,spulec/moto,william-richard/moto,william-richard/moto,william-richard/moto,spulec/moto