ShaderNetworkAlgoTest : Don't use six

We no longer support Python 2.

Author: johnhaddon

test/IECoreScene/ShaderNetworkAlgoTest.py

@@ -602,7 +602,7 @@ def testSplineInputs( self ):
 			output = "testSplines"
 		)
 
-		with six.assertRaisesRegex( self, Exception, r".*Cannot handle input to testSplines.fC3fcatmullRom\[0\].y.b : expanded spline has 33 control points, but max input adapter size is 32.*" ):
+		with self.assertRaisesRegex( Exception, r".*Cannot handle input to testSplines.fC3fcatmullRom\[0\].y.b : expanded spline has 33 control points, but max input adapter size is 32.*" ):
 			IECoreScene.ShaderNetworkAlgo.convertToOSLConventions( n, 11000 )
 
 		n = IECoreScene.ShaderNetwork(
@@ -619,7 +619,7 @@ def testSplineInputs( self ):
 			output = "testSplines"
 		)
 
-		with six.assertRaisesRegex( self, Exception, "Invalid spline point index xx" ):
+		with self.assertRaisesRegex( Exception, "Invalid spline point index xx" ):
 			IECoreScene.ShaderNetworkAlgo.convertToOSLConventions( n, 11000 )
 
 		n = IECoreScene.ShaderNetwork(
@@ -636,7 +636,7 @@ def testSplineInputs( self ):
 			output = "testSplines"
 		)
 
-		with six.assertRaisesRegex( self, Exception, "Spline index -1 is out of range in spline with 6 points." ):
+		with self.assertRaisesRegex( Exception, "Spline index -1 is out of range in spline with 6 points." ):
 			IECoreScene.ShaderNetworkAlgo.convertToOSLConventions( n, 11000 )
 
 		n = IECoreScene.ShaderNetwork(
@@ -653,7 +653,7 @@ def testSplineInputs( self ):
 			output = "testSplines"
 		)
 
-		with six.assertRaisesRegex( self, Exception, "Spline index 100 is out of range in spline with 6 points." ):
+		with self.assertRaisesRegex( Exception, "Spline index 100 is out of range in spline with 6 points." ):
 			IECoreScene.ShaderNetworkAlgo.convertToOSLConventions( n, 11000 )
 
 	def testColor4ComponentConnections( self ) :