bpo-35224: Bump the pyc magic number after the change in MAP_ADD (GH-14313)

Lib/importlib/_bootstrap_external.py

@@ -266,6 +266,8 @@ _code_type = type(_write_atomic.__code__)
 #     Python 3.8a1  3400 (move frame block handling to compiler #17611)
 #     Python 3.8a1  3401 (add END_ASYNC_FOR #33041)
 #     Python 3.8a1  3410 (PEP570 Python Positional-Only Parameters #36540)
+#     Python 3.8b2  3420 (Reverse evaluation order of key: value in dict
+#                         comprehensions #35224)
 #
 # MAGIC must change whenever the bytecode emitted by the compiler may no
 # longer be understood by older implementations of the eval loop (usually
@@ -274,7 +276,7 @@ _code_type = type(_write_atomic.__code__)
 # Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
 # in PC/launcher.c must also be updated.
 
-MAGIC_NUMBER = (3410).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3420).to_bytes(2, 'little') + b'\r\n'
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 
 _PYCACHE = '__pycache__'