Update core.py (pyparsing#259)

retsyo · web-flow · commit f10fcf8c98ea · 2021-01-03T16:37:00.000-06:00
since `pip install railroad` installs anthor package, I think it is better to point out the corrected one.
diff --git a/pyparsing/core.py b/pyparsing/core.py
@@ -1802,7 +1802,7 @@ def create_diagram(expr: "ParserElement", output_html, vertical=3, **kwargs):
             from .diagram import to_railroad, railroad_to_html
         except ImportError as ie:
             raise Exception(
-                "must install 'railroad' to generate parser railroad diagrams"
+                "must install 'Railroad-Diagram Generator' from https://pypi.org/project/railroad-diagrams to generate parser railroad diagrams"
             ) from ie
 
         railroad = to_railroad(expr, vertical=vertical, diagram_kwargs=kwargs)
