Sprinkle raw strings across the code base
    
    tox / pytest is complaining about lots and lots of invalid escape
    sequences in our code base. Sprinkle raw strings or backslash escapes
    across the code base to fix most occurences of:
    
      DeprecationWarning: invalid escape sequence
    
    There is still one warning that keeps repeating, though:
    
      source:264: DeprecationWarning: invalid escape sequence \d
    
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>