Merge pull request #2966 from joonro/history-extract-assert-msg

Added assert msg to extract_hist_ranges()

IPython/core/history.py

@@ -776,7 +776,7 b' def extract_hist_ranges(ranges_str):'
         endsess = rmatch.group("endsess") or startsess
         startsess = int(startsess.replace("~","-"))
         endsess = int(endsess.replace("~","-"))
-        assert endsess >= startsess
+        assert endsess >= startsess, "start session must be earlier than end session"
 
         if endsess == startsess:
             yield (startsess, start, end)