allow just the trailing Z for timezone

IPython/utils/jsonutil.py

@@ -33,7 +33,7 b" next_attr_name = '__next__' if py3compat.PY3 else 'next'"
 
 # timestamp formats
 ISO8601="%Y-%m-%dT%H:%M:%S.%f"
-ISO8601_PAT=re.compile(r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+(Z?[\+\-]\d{2}:?\d{2})?$")
+ISO8601_PAT=re.compile(r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+Z?([\+\-]\d{2}:?\d{2})?$")
 
 #-----------------------------------------------------------------------------
 # Classes and functions