Layers Unittest: Hidden flag to quckly update diffs

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This is not to be used lightly. But sometimes we change the name of the collections,
the initial value they have, ... and this helps to quickly update the tests.

tests/python/render_layer/render_layer_common.py

@@ -159,6 +159,7 @@ def dump(data):
 
 PDB = False
 DUMP_DIFF = True
+UPDATE_DIFF = False # HACK used to update tests when something change
 
 
 def compare_files(file_a, file_b):
@@ -172,6 +173,11 @@ def compare_files(file_a, file_b):
             import subprocess
             subprocess.call(["diff", "-u", file_a, file_b])
 
+        if UPDATE_DIFF:
+            import subprocess
+            subprocess.call(["cp", "-u", file_a, file_b])
+
+
         if PDB:
             import pdb
             print("Files differ:", file_a, file_b)