Add pragma on unreachable Windows code (#2041)

Author: Kludex

tests/importer/circular_import_a.py

@@ -1,4 +1,4 @@
 # Used by test_importer.py
 from .circular_import_b import foo  # noqa
 
-bar = 123
+bar = 123  # pragma: no cover

tests/importer/circular_import_b.py

@@ -1,4 +1,4 @@
 # Used by test_importer.py
 from .circular_import_a import bar  # noqa
 
-foo = 123
+foo = 123  # pragma: no cover

tests/test_auto_detection.py

@@ -11,8 +11,8 @@
 
 try:
     importlib.import_module("uvloop")
-    expected_loop = "uvloop"  # pragma: py-not-win32
-except ImportError:  # pragma: no cover
+    expected_loop = "uvloop"  # pragma: py-win32
+except ImportError:  # pragma: py-not-win32
     expected_loop = "asyncio"
 
 try: