Merge pull request openstenoproject#1500 from benoit-pierre/oslayer_c…

…leanups

oslayer: small cleanups

release 4.0.0.dev10

release 4.0.0.dev9

Merge pull request openstenoproject#929 from benoit-pierre/fix_926

gui_qt: fix possible crash on Linux

Merge pull request openstenoproject#872 from benoit-pierre/tweak_blac…

…kbox_assertion_message

utils: tweak blackbox test assertion message

bump development version