Fix anchor link from Good Practices to Pythonpath doc

Author: gene1wood

doc/en/goodpractices.rst

@@ -88,7 +88,7 @@ This has the following benefits:
 
 .. note::
 
-    See :ref:`pythonpath` for more information about the difference between calling ``pytest`` and
+    See :ref:`pytest vs python -m pytest` for more information about the difference between calling ``pytest`` and
     ``python -m pytest``.
 
 Note that using this scheme your test files must have **unique names**, because

doc/en/pythonpath.rst

@@ -72,6 +72,8 @@ imported in the global import namespace.
 
 This is also discussed in details in :ref:`test discovery`.
 
+.. _`pytest vs python -m pytest`:
+
 Invoking ``pytest`` versus ``python -m pytest``
 -----------------------------------------------