Traceback (most recent call last):
  File "site-packages/calibre/gui2/ui.py", line 158, in __init__
  File "site-packages/calibre/gui2/ui.py", line 172, in init_iaction
  File "site-packages/calibre/customize/__init__.py", line 614, in load_actual_plugin
  File "lib/python2.7/importlib/__init__.py", line 37, in import_module
  File "site-packages/calibre/gui2/actions/catalog.py", line 13, in <module>
  File "site-packages/calibre/gui2/tools.py", line 16, in <module>
  File "site-packages/calibre/gui2/convert/single.py", line 20, in <module>
  File "site-packages/calibre/gui2/convert/search_and_replace.py", line 11, in <module>
  File "site-packages/calibre/gui2/convert/search_and_replace_ui.py", line 155, in <module>
  File "site-packages/calibre/gui2/convert/regex_builder.py", line 18, in <module>
  File "site-packages/calibre/ebooks/conversion/search_replace.py", line 7, in <module>
  File "site-packages/regex/__init__.py", line 673, in <module>
  File "site-packages/regex/__init__.py", line 426, in _compile
  File "lib/python2.7/locale.py", line 562, in getlocale
  File "lib/python2.7/locale.py", line 475, in _parse_localename
ValueError: unknown locale: UTF-8