fixup! OpenColorIO : Defer expansion of context variables in OCIO vars

Because we are now using `Context::substitute()` on the values in the Context, we must use `/` rather than `\` for Windows paths, as `\` is an escape character. Is this too much of a change to make within Gaffer 1.4, even though `/` has always been our standard? I'm not sure, but I think one thing to factor into consideration is that it's probably fairly unlikely that anyone is setting the context in the way the unit tests do - and that all setting of the context via OpenColorIOConfigPlugs will need to have been using `/` already.

python/GafferImageTest/ColorSpaceTest.py

@@ -247,7 +247,7 @@ def testConfigFromGafferContext( self ) :
 
 		with Gaffer.Context() as c :
 
-			GafferImage.OpenColorIOAlgo.setConfig( c, str( self.openColorIOPath() / "context.ocio" ) )
+			GafferImage.OpenColorIOAlgo.setConfig( c, ( self.openColorIOPath() / "context.ocio" ).as_posix() )
 			GafferImage.OpenColorIOAlgo.addVariable( c, "LUT", "srgb.spi1d" )
 			GafferImage.OpenColorIOAlgo.addVariable( c, "CDL", "cineon.spi1d" )
 

python/GafferImageTest/DisplayTransformTest.py

@@ -256,7 +256,7 @@ def testDisplayAndViewDefaultToConfig( self ) :
 		explicitDisplayTransform["view"].setValue( config.getDefaultView( config.getDefaultDisplay() ) )
 
 		with Gaffer.Context() as context :
-			GafferImage.OpenColorIOAlgo.setConfig( context, str( configPath ) )
+			GafferImage.OpenColorIOAlgo.setConfig( context, configPath.as_posix() )
 			self.assertImagesEqual( defaultDisplayTransform["out"], explicitDisplayTransform["out"] )
 
 if __name__ == "__main__":

python/GafferImageTest/ImageReaderTest.py

@@ -524,7 +524,7 @@ def f( fileName, fileFormat, dataType, metadata, config ) :
 			( "exr", "openexr", "half", "" ),
 			( "dpx", "dpx", "uint12", "" ),
 			( "TIFF", "tiff", "float", "" ),
-			( "tif", "tiff", "uint32", str( self.openColorIOPath() / "context.ocio" ) ),
+			( "tif", "tiff", "uint32", ( self.openColorIOPath() / "context.ocio" ).as_posix() ),
 		] :
 
 			w["fileName"].setValue( self.temporaryDirectory() / "{0}.{1}".format( dataType, ext ) )

python/GafferImageTest/ImageWriterTest.py

@@ -1241,7 +1241,7 @@ def f( fileName, fileFormat, dataType, metadata, config ) :
 			( "exr", "openexr", "half", "" ),
 			( "dpx", "dpx", "uint12", "" ),
 			( "TIFF", "tiff", "float", "" ),
-			( "tif", "tiff", "uint32", str( self.openColorIOPath() / "context.ocio" ) ),
+			( "tif", "tiff", "uint32", ( self.openColorIOPath() / "context.ocio" ).as_posix() ),
 		] :
 
 			w["fileName"].setValue( self.temporaryDirectory() / "{0}.{1}".format( dataType, ext ) )

python/GafferImageTest/OpenColorIOAlgoTest.py

@@ -68,7 +68,7 @@ def testCurrentConfig( self ) :
 
 		with Gaffer.Context() as c :
 
-			GafferImage.OpenColorIOAlgo.setConfig( c, str( self.openColorIOPath() / "context.ocio" ) )
+			GafferImage.OpenColorIOAlgo.setConfig( c, ( self.openColorIOPath() / "context.ocio" ).as_posix() )
 			customConfig = GafferImage.OpenColorIOAlgo.currentConfig()
 			self.assertIsInstance( customConfig, PyOpenColorIO.Config )
 			self.assertEqual( customConfig.getCacheID(), PyOpenColorIO.Config.CreateFromFile( c["ocio:config"] ).getCacheID() )
@@ -89,7 +89,7 @@ def testCurrentConfigAndContext( self ) :
 
 		with Gaffer.Context() as c :
 
-			GafferImage.OpenColorIOAlgo.setConfig( c, str( self.openColorIOPath() / "context.ocio" ) )
+			GafferImage.OpenColorIOAlgo.setConfig( c, ( self.openColorIOPath() / "context.ocio" ).as_posix() )
 			GafferImage.OpenColorIOAlgo.addVariable( c, "LUT", "srgb.spi1d" )
 
 			customConfig, customContext = GafferImage.OpenColorIOAlgo.currentConfigAndContext()