MAINT: Bump AppVeyor to 3.7 (#575)
MAINT: Bump AppVeyor to 3.7 (#575)

* MAINT: Bump AppVeyor to 3.7

* FIX: prompt_toolkit

* FIX: Try again

* FIX?

* FIX?

* FIX?

* FIX?

* FIX?

* FIX?

Eric89GXL/sphinx-gallery,Titan-C/sphinx-gallery,sphinx-gallery/sphinx-gallery,Titan-C/sphinx-gallery,Eric89GXL/sphinx-gallery,sphinx-gallery/sphinx-gallery