EOFError when cwd(back)

When using put() with a path having more than one slash, i have had EOFErrror.
File ftpretty.py
It happens on line 135 self.conn.cwd(back)
It was a python issue: .cwd('..') works, .cwd('../..') works, but .cwd('../../..') and longer does'nt

I replaced lines 134 & 135 with for _ in range(depth):self.conn.cwd('..') and don't have any issue since

