Make issue680 test succeed with LC_ALL=C

Previously, it was failing with:

nose.proxy.UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2
in position 189: ordinal not in range(128)
Merge pull request #788 from mitya57/master

Make issue680 test succeed with LC_ALL=C
Disable test_concurrent_shared.

It simply causes too many problems with Travis and other build farms.