Bug#888311: Locale not found message

[David Cortes]

Package: playonlinux
Version: 4.2.10-2

When using 'Detailed Settings' in KDE's regional options (in  
systemsettings5 --> Regional Settings --> Format --> Check on 'Detailed  
Settings), applications installed with playonlinux throw a 'Wrapper Error'  
message about the locale – in my case, it reads like this:
"locale 'en_US' cannot be set"

My settings in KDE regional settings are as follows:
-Region: United States -American English (en_US)
-Time: Germany - English (en_DE)
-Rest: set to 'No change'