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>

ipaserver/plugins/migration.py

@@ -469,7 +469,7 @@ def construct_filter(template, oc_list):
     return template % oc_subfilter
 
 def validate_ldapuri(ugettext, ldapuri):
-    m = re.match('^ldaps?://[-\w\.]+(:\d+)?$', ldapuri)
+    m = re.match(r'^ldaps?://[-\w\.]+(:\d+)?$', ldapuri)
     if not m:
         err_msg = _('Invalid LDAP URI.')
         raise errors.ValidationError(name='ldap_uri', error=err_msg)