Backport changes pyinstaller/pyinstaller#5291 (#65)

New pytest markers were introduced in pyinstaller/pyinstaller#5291:

 - @pytest.mark.darwin (only runs on macOS)
 - @pytest.mark.linux (only runs on GNU/Linux)
 - @pytest.mark.win32 (only runs  on Windows)

src/_pyinstaller_hooks_contrib/tests/test_libraries.py

@@ -13,7 +13,7 @@
 import pytest
 
 from PyInstaller.compat import is_darwin, is_win
-from PyInstaller.utils.tests import importorskip, xfail, skipif_win
+from PyInstaller.utils.tests import importorskip, xfail
 from PyInstaller.utils.hooks import is_module_satisfies
 
 
@@ -252,7 +252,8 @@ def test_pinyin(pyi_builder):
 
 
 @importorskip('uvloop')
-@skipif_win
+@pytest.mark.darwin
+@pytest.mark.linux
 def test_uvloop(pyi_builder):
     pyi_builder.test_source("import uvloop")