Duh. cmdqueue should be an instance variable, not a class variable.

This was introduced in 1998 in rev. 1.13, where I imported extensive
patches that, I am sad to say, I didn't review as carefully as I
should have.

Lib/cmd.py

@@ -68,7 +68,6 @@ class Cmd:
     identchars = IDENTCHARS
     ruler = '='
     lastcmd = ''
-    cmdqueue = []
     intro = None
     doc_leader = ""
     doc_header = "Documented commands (type help <topic>):"
@@ -86,6 +85,7 @@ class Cmd:
         automatically.
 
         """
+        self.cmdqueue = []
         if completekey:
             try:
                 import readline