remove dead code

Initially added in commit c1ef643b8ed6c1740438692e345761a401fea1af but I
cannot tell what it was ever used for.

src/calibre/utils/sftp.py

@@ -1,90 +0,0 @@
-#!/usr/bin/env  python2
-from __future__ import print_function
-__license__   = 'GPL v3'
-__copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
-__docformat__ = 'restructuredtext en'
-
-'''
-Create a file handle to a remote file over the sftp protocol.
-'''
-
-import sys, socket, getpass
-from urlparse import urlparse
-from binascii import hexlify
-
-import paramiko
-
-
-def agent_auth(transport, username):
-    """
-    Attempt to authenticate to the given transport using any of the private
-    keys available from an SSH agent.
-    """
-
-    agent = paramiko.Agent()
-    agent_keys = agent.get_keys()
-    if len(agent_keys) == 0:
-        return
-
-    for key in agent_keys:
-        print('Trying ssh-agent key %s' % hexlify(key.get_fingerprint()), end=' ')
-        try:
-            transport.auth_publickey(username, key)
-            print('... success!')
-            return True
-        except paramiko.SSHException:
-            print('... failed.')
-    return False
-
-
-def portable_getpass(username, hostname, retry):
-    return getpass.getpass('%sPlease enter the password for %s on %s: '%(
-                                'Incorrect password. ' if retry else '', username, hostname))
-
-
-def password_auth(transport, username, hostname, getpw=portable_getpass):
-    for i in range(3):
-        pw = getpw(username, hostname, i>0)
-        transport.auth_password(username, pw)
-        if transport.is_authenticated():
-            return True
-    return False
-
-
-def connect_to_url(url, getpw=portable_getpass, mode='r+', bufsize=-1):
-    protocol, host, path = urlparse(url)[:3]
-    if protocol != 'sftp':
-        raise ValueError(_('URL must have the scheme sftp'))
-    try:
-        username, host = host.split('@')
-    except:
-        raise ValueError(_('host must be of the form user@hostname'))
-    port = 22
-    if ':' in host:
-        host, port = host.split(':')
-        port = int(port)
-    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-    sock.connect((host, port))
-    t = paramiko.Transport(sock)
-    try:
-        t.start_client()
-    except:
-        raise Exception(_('Failed to negotiate SSH session: ') + str(t.get_exception()))
-    if not agent_auth(t, username):
-        if not password_auth(t, username, host, getpw):
-            raise ValueError(_('Failed to authenticate with server: %s')%url)
-    sftp = paramiko.SFTPClient.from_transport(t)
-    return sftp, sftp.open(path, mode=mode, bufsize=bufsize)
-
-
-def main(args=sys.argv):
-    f = connect_to_url(args[1])[-1]
-    print(f.read())
-    f.seek(0, 2)
-    print(f.tell())
-    f.close()
-    return 0
-
-
-if __name__ == '__main__':
-    sys.exit(main())