And now add the Draft7 time format, even though it don't work.

Because FormatChecker is bad and I should feel bad :/

This is currently being overriden by the older Draft3 time
format.

Probably time to deprecate cls_checks, and pass format checkers
in on validator creation.

The changes in #425 are likely also relevant.

Author: Julian

jsonschema/_format.py

@@ -278,6 +278,13 @@ def is_datetime(instance):
         return strict_rfc3339.validate_rfc3339(instance)
 
 
+    @_checks_drafts(draft7="time")
+    def is_time(instance):
+        if not isinstance(instance, str_types):
+            return True
+        return is_datetime("1970-01-01T" + instance)
+
+
 @_checks_drafts(name="regex", raises=re.error)
 def is_regex(instance):
     if not isinstance(instance, str_types):