On a system with no ssl module the following test failure occurs:

======================================================================
ERROR: test_dir (test.test_ftplib.TestFTPClass)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/rkackley/Code/cpython/Lib/test/test_ftplib.py", line 598, in test_dir
    self.client.dir(lambda x: l.append(x))
  File "/home/rkackley/Code/cpython/Lib/ftplib.py", line 565, in dir
    self.retrlines(cmd, func)
  File "/home/rkackley/Code/cpython/Lib/ftplib.py", line 476, in retrlines
    if isinstance(conn, _SSLSocket):
TypeError: isinstance() arg 2 must be a type or tuple of types