Update bdb.py from CPython v3.12.0

Lib/bdb.py

@@ -570,9 +570,12 @@ class Bdb:
             rv = frame.f_locals['__return__']
             s += '->'
             s += reprlib.repr(rv)
-        line = linecache.getline(filename, lineno, frame.f_globals)
-        if line:
-            s += lprefix + line.strip()
+        if lineno is not None:
+            line = linecache.getline(filename, lineno, frame.f_globals)
+            if line:
+                s += lprefix + line.strip()
+        else:
+            s += f'{lprefix}Warning: lineno is None'
         return s
 
     # The following methods can be called by clients to use
@@ -805,15 +808,18 @@ def checkfuncname(b, frame):
     return True
 
 
-# Determines if there is an effective (active) breakpoint at this
-# line of code.  Returns breakpoint number or 0 if none
 def effective(file, line, frame):
-    """Determine which breakpoint for this file:line is to be acted upon.
+    """Return (active breakpoint, delete temporary flag) or (None, None) as
+       breakpoint to act upon.
 
-    Called only if we know there is a breakpoint at this location.  Return
-    the breakpoint that was triggered and a boolean that indicates if it is
-    ok to delete a temporary breakpoint.  Return (None, None) if there is no
-    matching breakpoint.
+       The "active breakpoint" is the first entry in bplist[line, file] (which
+       must exist) that is enabled, for which checkfuncname is True, and that
+       has neither a False condition nor a positive ignore count.  The flag,
+       meaning that a temporary breakpoint should be deleted, is False only
+       when the condiion cannot be evaluated (in which case, ignore count is
+       ignored).
+
+       If no such entry exists, then (None, None) is returned.
     """
     possibles = Breakpoint.bplist[file, line]
     for b in possibles: