Runtime Imports cause thread deadlock
*Created originally on Bitbucket by [legonigel (Nigel Armstrong)](https://bitbucket.org/%7Bdc2e7037-98e3-4d14-8ad6-960683af7f34%7D/)* Inside `workbook.py` there are some runtime imports in the `_setup_styles(self)` method. When this method is run from a second thread it can in some cases cause deadlock due to the import lock. If these imports are done at import time, this issue should go away. It looks to me that these imports are in the function to control the scope of the imports. An alternative might be to use `from ... import ... as ...` and maybe use and `_name` to control the import.
issue