Fix invalid escape sequence warning
Fix invalid escape sequence warning

Python 3.6 is more strict about special characters in regular strings if
they are invalid escape sequences. This most often happens in regex
strings. This fixes one instance by switching the regex string to use a
raw string.

Change-Id: I73a7393fe04c920c7d82a2fa68f1cf0c7d453a7d
Signed-off-by: Sean McGinnis <961eeb09b6d45516665e15b82e013282c4faf575@gmail.com>

openstack/oslo.vmware