az feedback auto-generates most of the information requested below, as of CLI version 2.0.62

Describe the bug
Network module's vnet commands are broken in the latest dev branch. Calling any command from the module fails bcz of a code error.

To Reproduce
az network vnet {create, list}

Both fail with:
(env) PS D:\azure-cli> az network vnet list
The command failed with an unexpected error. Here is the traceback:

'NoneType' object has no attribute 'standard_medium'
Traceback (most recent call last):
File "D:\azure-cli\env\lib\site-packages\knack\cli.py", line 215, in invoke
cmd_result = self.invocation.execute(args)
File "d:\azure-cli\src\azure-cli-core\azure\cli\core\commands_init_.py", line 553, in execute
self.commands_loader.load_arguments(command)
File "d:\azure-cli\src\azure-cli-core\azure\cli\core_init_.py", line 446, in load_arguments
loader.load_arguments(command) # this adds entries to the argument registries
File "d:\azure-cli\src\azure-cli\azure\cli\command_modules\network_init_.py", line 39, in load_arguments
load_arguments(self, command)
File "d:\azure-cli\src\azure-cli\azure\cli\command_modules\network_params.py", line 123, in load_arguments
c.argument('sku', arg_group='Gateway', help='The name of the SKU.', arg_type=get_enum_type(ApplicationGatewaySkuName), default=ApplicationGatewaySkuName.standard_medium.value)
AttributeError: 'NoneType' object has no attribute 'standard_medium'

Expected behavior
The command should throw error for the lack of parameters provided. If all the params are provided the command should succeed.

Environment summary
CLI version
(env) PS D:\azure-cli> az --version
azure-cli 2.8.0

command-modules-nspkg 2.0.3
core 2.8.0
nspkg 3.0.4
telemetry 1.0.4
testsdk 0.2.4

Extensions:
virtual-wan 0.1.3

Python location 'D:\azure-cli\env\Scripts\python.exe'
Extensions directory 'C:\Users\mekaushi.azure\cliextensions'

Python (Windows) 3.8.2 (tags/v3.8.2:7b3ab59, Feb 25 2020, 22:45:29) [MSC v.1916 32 bit (Intel)]

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Additional context