Add another open issue.

pep-0553.rst

@@ -101,6 +101,15 @@ Does it make sense to define the built-in function's signature as
 would allow users to pass useful arguments to their actual debugger.
 This isn't useful for ``pdb`` but might be useful for alternatives.
 
+Should we add an environment variable so that ``sys.breakpointhook()`` can be
+set outside of the Python invocation?  E.g.::
+
+    $ export PYTHONBREAKPOINTHOOK=my.debugger:Debugger
+
+This would provide execution environments such as IDEs which run Python code
+inside them, to set an internal breakpoint hook before any Python code
+executes.
+
 
 Implementation
 ==============