Unable to import GrayScale Textures

Reported by Twitter user,

"Does #UE4 seriously not support importing greyscale textures anymore?"

1) Open a Project in UE4Editor
2) Select Import in Content Browser
3) Select either of the attached files

Results
LogAssetTools:Warning: Failed to import '/Users/.../Desktop/GrayScale.tga'. Failed to create asset '/Game/GrayScale'

Error when importing grayscale .tga files