diff --git a/homeassistant/components/notify/twilio_call.py b/homeassistant/components/notify/twilio_call.py
index 37068d6e220..59da15aeebc 100644
--- a/homeassistant/components/notify/twilio_call.py
+++ b/homeassistant/components/notify/twilio_call.py
@@ -46,47 +46,47 @@ def is_validurl(url):
     """Check if the passed url is valid using dperini regex."""
     import re
 
-    ip_middle_oct = u"(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5]))"
-    ip_last_oct = u"(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))"
+    ip_middle_oct = r"(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5]))"
+    ip_last_oct = r"(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))"
 
     regex = re.compile(
-        u"^"
+        r"^"
         # protocol identifier
-        u"(?:(?:https?|ftp)://)"
+        r"(?:(?:https?|ftp)://)"
         # user:pass authentication
-        u"(?:\S+(?::\S*)?@)?"
-        u"(?:"
-        u"(?P<private_ip>"
+        r"(?:\S+(?::\S*)?@)?"
+        r"(?:"
+        r"(?P<private_ip>"
         # IP address exclusion
         # private & local networks
-        u"(?:(?:10|127)" + ip_middle_oct + u"{2}" + ip_last_oct + u")|"
-        u"(?:(?:169\.254|192\.168)" + ip_middle_oct + ip_last_oct + u")|"
-        u"(?:172\.(?:1[6-9]|2\d|3[0-1])" + ip_middle_oct + ip_last_oct + u"))"
-        u"|"
+        r"(?:(?:10|127)" + ip_middle_oct + u"{2}" + ip_last_oct + u")|"
+        r"(?:(?:169\.254|192\.168)" + ip_middle_oct + ip_last_oct + u")|"
+        r"(?:172\.(?:1[6-9]|2\d|3[0-1])" + ip_middle_oct + ip_last_oct + u"))"
+        r"|"
         # IP address dotted notation octets
         # excludes loopback network 0.0.0.0
         # excludes reserved space >= 224.0.0.0
         # excludes network & broadcast addresses
         # (first & last IP address of each class)
-        u"(?P<public_ip>"
-        u"(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])"
-        u"" + ip_middle_oct + u"{2}"
-        u"" + ip_last_oct + u")"
-        u"|"
+        r"(?P<public_ip>"
+        r"(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])"
+        r"" + ip_middle_oct + u"{2}"
+        r"" + ip_last_oct + u")"
+        r"|"
         # host name
-        u"(?:(?:[a-z\u00a1-\uffff0-9]-?)*[a-z\u00a1-\uffff0-9]+)"
+        r"(?:(?:[a-z\u00a1-\uffff0-9]-?)*[a-z\u00a1-\uffff0-9]+)"
         # domain name
-        u"(?:\.(?:[a-z\u00a1-\uffff0-9]-?)*[a-z\u00a1-\uffff0-9]+)*"
+        r"(?:\.(?:[a-z\u00a1-\uffff0-9]-?)*[a-z\u00a1-\uffff0-9]+)*"
         # TLD identifier
-        u"(?:\.(?:[a-z\u00a1-\uffff]{2,}))"
-        u")"
+        r"(?:\.(?:[a-z\u00a1-\uffff]{2,}))"
+        r")"
         # port number
-        u"(?::\d{2,5})?"
+        r"(?::\d{2,5})?"
         # resource path
-        u"(?:/\S*)?"
+        r"(?:/\S*)?"
         # query string
-        u"(?:\?\S*)?"
-        u"$",
+        r"(?:\?\S*)?"
+        r"$",
         re.UNICODE | re.IGNORECASE
     )