Sad to come back here today again, but it seems that my problems doesn't end after #189.
Theme manager and UAS looks fine for now, but can't use LogViewer.
OS: Windows 10 x64
System-Wide language: Russian
Codepage: 1251
Locale: 1251

2016-07-14 17:11:27,227 (600) : DEBUG (logkit:13) - Fatal error happened in Logs show: 'utf8' codec can't decode byte 0xce in position 94: invalid continuation byte
Code reference:
Contents.Code.logs.logs#show:123
Worth to mention, that it works fine on my virtualbox with Linux Mint 18 and utf-8 by default.
wt_log_logviewer_error.zip