I added the following two lines and I was able to run the code.


Before: 
            line = fp.readline()
            if self.debugging > 2: print('*retr*', repr(line))
            if not line:
                break
            if line[-2:] == CRLF:
                line = line[:-2]
            elif line[-1:] == '\n':
                line = line[:-1]
            callback(line)

After: 
            line = fp.readline()
            if self.debugging > 2: print('*retr*', repr(line))
            if not line:
                break
            if line == '':
                break
            if line[-2:] == CRLF:
                line = line[:-2]
            elif line[-1:] == '\n':
                line = line[:-1]
            callback(line)

As a patch:

426,427d425
<             if line == '':
<                 break

What else do I need to do?