[PATCH] tests/cmdline/: Do not import "string" library when it isnot used

Hello,

Please find attached the patch for review. Please confirm if i can
commit this.
[[
Patch by: bhuvan
Do not import "string" library when it is not used.

[in subversion/tests/cmdline/]
* revert_tests.py
* trans_tests.py
* externals_tests.py
* lock_tests.py
* history_tests.py
* switch_tests.py
* copy_tests.py
* stat_tests.py
* schedule_tests.py
* prop_tests.py
* export_tests.py
* utf8_tests.py
* merge_tests.py
* getopt_tests.py
  Do not import "string" library when it is not used.
]]

-- 
Regards,
Bhuvaneswaran