Thanks for the output and good to see it is working cleanly now.
Actually the problem you had in your previous post was that the board was set to the Arduino Yun because the system was confused after the install changes. It sorted itself out after restarting the ide or by re-selecting the board on the tool bar. This doesn't happen often, sometimes after changing install/config, a fix is being worked on at the moment.
You can see this in the original compile for the Arduino Yun which is always the first board in the list. It wasn't easy to see because you had the diagnostics switched on:-
Compiling 'WICED_MPL3115A2_AIO_Test' for 'Arduino Yún'
Then when it worked you could see this:-
Compiling 'WICED_MPL3115A2_AIO_Test' for 'Adafruit WICED Feather'
Installing the MQTT lib certainly caused the last compile error because it overrode the mqtt that is installed with the feather config. I will look into if the rules should have changed in that area or not.
One thing that strikes me is that now you have reinstalled your arduino and I assume your feather hardware config the uploader statement has completely changed.
Where previously it was making a python call now it runs the feather_dfu.exe so this might be an indication that the toolchain is still developing. I will try to get hold of a board and monitor its progress.
Uploading via Bootloader
C:\Users\[your_name]her_dfu\feather_dfu.exe -u "C:\Users\[your_name]util/dfu-util-static.exe" arduino_upgrade "C:\Users\[your_name]\AppData\Local\Temp\VMicroBuilds\[your_name]_WICED_MPL3115A2_AIO_Test\Adafruit_WICED_Arduino_feather/[your_name]_WICED_MPL3115A2_AIO_Test.ino.bin"
dfu-util 0.8
One last question Can you confirm if you have the board.txt setting for upload.8dot3=false? If so does it still upload okay if you set upload.8dot3=true
Thanks very much and well done for persisting.