errors: make exit codes class variables instead

Kyle pointed out to me that we can simply make the exit codes class
variables. Python provides some magic for making them accessible as
instance variables.

This also makes it easier to let subclasses of existing errors
override the exit codes by letting them simply define their own values
as class variables. That means that there's no need to pass them into
the superclass's constructor arguments, so the superclass doesn't need
to expose the them as arguments. (Making a subclass set a different
exit code for a subclass of `StorageError` was actually the goal with
my recent series.)

Differential Revision: https://phab.mercurial-scm.org/D10758

mercurial/error.py

@@ -54,14 +54,13 b' class Hint(object):'
 class Error(Hint, Exception):
     """Base class for Mercurial errors."""
 
-    def __init__(
-        self, message, hint=None, coarse_exit_code=None, detailed_exit_code=None
-    ):
+    coarse_exit_code = None
+    detailed_exit_code = None
+
+    def __init__(self, message, hint=None):
         # type: (bytes, Optional[bytes]) -> None
         self.message = message
         self.hint = hint
-        self.coarse_exit_code = coarse_exit_code
-        self.detailed_exit_code = detailed_exit_code
         # Pass the message into the Exception constructor to help extensions
         # that look for exc.args[0].
         Exception.__init__(self, message)
@@ -97,10 +96,7 b' class StorageError(Error):'
     Usually subclassed by a storage-specific exception.
     """
 
-    def __init__(self, message, hint=None):
-        super(StorageError, self).__init__(
-            message, hint=hint, detailed_exit_code=50
-        )
+    detailed_exit_code = 50
 
 
 class RevlogError(StorageError):
@@ -205,10 +201,8 b' class WorkerError(Exception):'
 class InterventionRequired(Abort):
     """Exception raised when a command requires human intervention."""
 
-    def __init__(self, message, hint=None):
-        super(InterventionRequired, self).__init__(
-            message, hint=hint, coarse_exit_code=1, detailed_exit_code=240
-        )
+    coarse_exit_code = 1
+    detailed_exit_code = 240
 
     def format(self):
         # type: () -> bytes
@@ -243,10 +237,7 b' class InputError(Abort):'
     Examples: Invalid command, invalid flags, invalid revision.
     """
 
-    def __init__(self, message, hint=None):
-        super(InputError, self).__init__(
-            message, hint=hint, detailed_exit_code=10
-        )
+    detailed_exit_code = 10
 
 
 class StateError(Abort):
@@ -255,10 +246,7 b' class StateError(Abort):'
     Examples: Unresolved merge conflicts, unfinished operations.
     """
 
-    def __init__(self, message, hint=None):
-        super(StateError, self).__init__(
-            message, hint=hint, detailed_exit_code=20
-        )
+    detailed_exit_code = 20
 
 
 class CanceledError(Abort):
@@ -267,10 +255,7 b' class CanceledError(Abort):'
     Examples: Close commit editor with error status, quit chistedit.
     """
 
-    def __init__(self, message, hint=None):
-        super(CanceledError, self).__init__(
-            message, hint=hint, detailed_exit_code=250
-        )
+    detailed_exit_code = 250
 
 
 class SecurityError(Abort):
@@ -280,10 +265,7 b' class SecurityError(Abort):'
     filesystem, mismatched GPG signature, DoS protection.
     """
 
-    def __init__(self, message, hint=None):
-        super(SecurityError, self).__init__(
-            message, hint=hint, detailed_exit_code=150
-        )
+    detailed_exit_code = 150
 
 
 class HookLoadError(Abort):
@@ -297,20 +279,17 b' class HookAbort(Abort):'
 
     Exists to allow more specialized catching."""
 
-    def __init__(self, message, hint=None):
-        super(HookAbort, self).__init__(
-            message, hint=hint, detailed_exit_code=40
-        )
+    detailed_exit_code = 40
 
 
 class ConfigError(Abort):
     """Exception raised when parsing config files"""
 
+    detailed_exit_code = 30
+
     def __init__(self, message, location=None, hint=None):
         # type: (bytes, Optional[bytes], Optional[bytes]) -> None
-        super(ConfigError, self).__init__(
-            message, hint=hint, detailed_exit_code=30
-        )
+        super(ConfigError, self).__init__(message, hint=hint)
         self.location = location
 
     def format(self):
@@ -357,10 +336,7 b' class ResponseExpected(Abort):'
 class RemoteError(Abort):
     """Exception raised when interacting with a remote repo fails"""
 
-    def __init__(self, message, hint=None):
-        super(RemoteError, self).__init__(
-            message, hint=hint, detailed_exit_code=100
-        )
+    detailed_exit_code = 100
 
 
 class OutOfBandError(RemoteError):
@@ -380,11 +356,11 b' class OutOfBandError(RemoteError):'
 class ParseError(Abort):
     """Raised when parsing config files and {rev,file}sets (msg[, pos])"""
 
+    detailed_exit_code = 10
+
     def __init__(self, message, location=None, hint=None):
         # type: (bytes, Optional[Union[bytes, int]], Optional[bytes]) -> None
-        super(ParseError, self).__init__(
-            message, hint=hint, detailed_exit_code=10
-        )
+        super(ParseError, self).__init__(message, hint=hint)
         self.location = location
 
     def format(self):