Print what shader is loading so we have a chance to debug stuff

Author: einarf

demosys/loaders/program/single.py

@@ -10,6 +10,8 @@ def load(self):
         if not self.meta.resolved_path:
             raise ValueError("Cannot find program '{}'".format(self.meta.path))
 
+        print("Loading:", self.meta.path)
+
         with open(self.meta.resolved_path, 'r') as fd:
             shaders = program.ProgramShaders.from_single(self.meta, fd.read())