Add event codes list for "github" application

github/event_codes.py

@@ -0,0 +1,26 @@
+import enum
+
+
+EventCode = enum.IntEnum(
+    value="EventCode",
+    # New names should only be added to the *end* of this list.
+    # Adding a new name will implicitly change the integer value of
+    # the names that come after it, which will change how these are
+    # aggregated in our log files.
+    #
+    # For the same reason, once an event code has been released into
+    # production, it should not be removed from the list.
+    names=[
+        'SignatureNotSha1',
+        'PostDataMissing',
+        'InvalidSignature',
+        'UnsupportedGithubEvent',
+        'UnsupportedAction',
+        'ReleaseAttributeMissing',
+    ],
+    # This start value is designed to be unique for the "github" app.
+    # Other apps should use a different start value that does not
+    # reasonably conflict with this value (e.g. 2000, 3000, and so
+    # on).
+    start=1000,
+)