Don't lie in __all__ attributes when SSL is not available: only add the SSL
classes when they are actually created.
diff --git a/Lib/poplib.py b/Lib/poplib.py
index 58ebb50..c421529 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -15,7 +15,7 @@
 
 import re, socket
 
-__all__ = ["POP3","error_proto","POP3_SSL"]
+__all__ = ["POP3","error_proto"]
 
 # Exception raised when an error or invalid response is received:
 
@@ -397,6 +397,7 @@
             del self.sslobj, self.sock
             return resp
 
+    __all__.append("POP3_SSL")
 
 if __name__ == "__main__":
     import sys