Wrong cache_dir variable (session_mirror.py)

[jhuguetn]

Wrong use of scan_cache_dir path variable at copy_session() when traversing across session resources at mirroring process. See here:

pyxnat/bin/sessionmirror.py

Line 491 in 53e7eb9

res_cache_dir = op.join(scan_cache_dir, res_label)

Throwing the following error,

Traceback (most recent call last):
  File "sessionmirror.py", line 711, in <module>
    main(args)
  File "sessionmirror.py", line 705, in main
    copy_session(src_sess, dst_sess, '/tmp')
  File "sessionmirror.py", line 491, in copy_session
    res_cache_dir = op.join(scan_cache_dir, res_label)
UnboundLocalError: local variable 'scan_cache_dir' referenced before assignment

Fix proposal

Use session_cache_dir instead.