Tests fail on Windows due to 'diff'

[hustf]

After running Pkg.test("Compose") on Julia 0.4.6 and Windows the message below appears.

Shell commands and windows don't work well currently (depending on individual PATH settings, which are not so popular on Windows). I don't know about any good alternatives to disabling this test with something like

is_unix() &&

ERROR: LoadError: LoadError: could not spawn `diff 'C:\Users\F\.julia\v0.4\Compose\test\data\text.png' 'C:\Users\F\.julia\v0.4\Compose\test\text.png'`: no such file or directory (ENOENT)
 in _jl_spawn at process.jl:262
while loading C:\Users\F\.julia\v0.4\Compose\test\compare_examples.jl, in expression starting on line 32
while loading C:\Users\F\.julia\v0.4\Compose\test\runtests.jl, in expression starting on line 18
===================================================[ ERROR: Compose ]===================================================

failed process: Process(`'C:\Users\F\AppData\Local\Julia-0.4.6\bin\julia' --check-bounds=yes --code-coverage=none --color=yes 'C:\Users\F\.julia\v0.4\Compose\test\runtests.jl'`, ProcessExited(1)) [1]

========================================================================================================================
INFO: No packages to install, update or remove
ERROR: Compose had test errors
 in error at error.jl:21