USD Tests : Use lowercase drive letter on Windows

USD is inconsistent on the case of the drive letter when returning Windows paths. Windows is not case-sensitive, so we can safely correct case in tests.

Author: ericmehl

contrib/IECoreUSD/test/IECoreUSD/SceneCacheFileFormatTest.py

@@ -1083,7 +1083,10 @@ def testLinksTimeOffset( self ):
 			valueClip = pxr.Usd.ClipsAPI( offsetPrim )
 			clip = valueClip.GetClips()["default"]
 
-			self.assertEqual( clip["assetPaths"], pxr.Sdf.AssetPathArray( [pxr.Sdf.AssetPath( fileName, fileName )] ) )
+			self.assertEqual(
+				[ os.path.normcase( str( p ) ) for p in clip["assetPaths"] ],
+				[ os.path.normcase( str( p ) ) for p in pxr.Sdf.AssetPathArray( [ pxr.Sdf.AssetPath( fileName, fileName ) ] ) ]
+			)
 			self.assertEqual( clip["primPath"], "/{}".format( IECoreUSD.SceneCacheDataAlgo.internalRootName() ) )
 
 			self.assertEqual( clip["times"], pxr.Vt.Vec2dArray( [ pxr.Gf.Vec2d( start * fps, fps ), pxr.Gf.Vec2d( end * fps, 2.0 * fps ) ] ) )

contrib/IECoreUSD/test/IECoreUSD/USDSceneTest.py

@@ -2968,16 +2968,16 @@ def testTextureParameters( self ) :
 
 		self.assertEqual( network.size(), 4 )
 		self.assertEqual(
-			os.path.normpath( network.getShader( "relativeTexture" ).parameters["file"].value ),
-			os.path.join( os.path.dirname( __file__ ), "myTexture.tx" ),
+			os.path.normcase( os.path.normpath( network.getShader( "relativeTexture" ).parameters["file"].value ) ),
+			os.path.normcase( os.path.join( os.path.dirname( __file__ ), "myTexture.tx" ) ),
 		)
 		self.assertEqual(
-			os.path.normpath( network.getShader( "relativeUDIMTexture" ).parameters["file"].value ),
-			os.path.join( os.path.dirname( __file__ ), "myTexture.<UDIM>.tx" ),
+			os.path.normcase( os.path.normpath( network.getShader( "relativeUDIMTexture" ).parameters["file"].value ) ),
+			os.path.normcase( os.path.normpath( os.path.join( os.path.join( os.path.dirname( __file__ ) ), "myTexture.<UDIM>.tx" ) ) ),
 		)
 		self.assertEqual(
-			os.path.normpath( network.getShader( "udimTexture" ).parameters["file"].value ),
-			os.path.normpath( "/full/path/to/myTexture.<UDIM>.tx" )
+			os.path.normcase( os.path.normpath( network.getShader( "udimTexture" ).parameters["file"].value ) ),
+			os.path.normcase( os.path.normpath( "/full/path/to/myTexture.<UDIM>.tx" ) )
 		)
 
 	def testExposedShaderInput( self ) :