Error building assembly … cannot find metadata file in Cities: Skylines

Issue

Errors building assembly c:\Users\YOUR_USER_NAME\AppData\Local\Colossal Order\Cities_Skylines\Addons\Mods\MY_MIX_NAME
(0,0): error CS0006: cannot find metadata flie ‘…steamapps\common\Cities_Skylines\Cities_Data\Managed’
(0,0): error CS0006: cannot find metadata flie ‘…steamapps\common\Cities_Skylines\Cities_Data\Managed’

Cause

The Theme Mixer 2 causes this error if you try to export a mix.

Even if you uninstall the mod, every time the game starts, the message appears in the Debug Output.

Solution

Delete the MY_MIX_NAME directory you find in the “C:\Users\YOUR_USER_NAME\AppData\Local\Colossal Order\Cities_Skylines\Addons\Mods” folder