show interface status, show platform summary and other cmds are broken

[nikos-github]

The #298 commit is breaking show commands for any port_config.ini that doesn't have an alias in it.

Alias is optional in sonic.

This is a blocker since platform/OS stability is compromised and identification as well as status for deployment is not possible.

show interface status error:

root@sonic:/# show interface status
Traceback (most recent call last):
File "/usr/bin/show", line 9, in
load_entry_point('sonic-utilities==1.2', 'console_scripts', 'show')()
File "/usr/lib/python2.7/dist-packages/pkg_resources/init.py", line 561, in load_entry_point
return get_distribution(dist).load_entry_point(group, name)
File "/usr/lib/python2.7/dist-packages/pkg_resources/init.py", line 2631, in load_entry_point
return ep.load()
File "/usr/lib/python2.7/dist-packages/pkg_resources/init.py", line 2291, in load
return self.resolve()
File "/usr/lib/python2.7/dist-packages/pkg_resources/init.py", line 2297, in resolve
module = import(self.module_name, fromlist=['name'], level=0)
File "/usr/lib/python2.7/dist-packages/show/main.py", line 199, in
iface_alias_converter = InterfaceAliasConverter()
File "/usr/lib/python2.7/dist-packages/show/main.py", line 64, in init
self.port_dict[port_name]['alias']):
KeyError: 'alias'

show platform summary syslog error:
Dec 05 05:08:31 spine-1 aos[5216]: iface_alias_converter = InterfaceAliasConverter()
Dec 05 05:08:31 spine-1 aos[5216]: File "/usr/lib/python2.7/dist-packages/show/main.py", line 64, in init
Dec 05 05:08:31 spine-1 aos[5216]: self.port_dict[port_name]['alias']):
Dec 05 05:08:31 spine-1 aos[5216]: KeyError: 'alias'

[jleveque]

@paavaanan, @padmanarayana: Please add logic to check for the existence of the "alias" field before all attempts to access it in order to prevent this crash.

Per our spec, https://github.com/Azure/SONiC/wiki/Configuration, the 'alias' field is optional in ConfigDB. Therefore, we must gracefully handle the case where it doesn't exist.

[nikos-github]

Fixed by #405. Fix to verified once we have our new internal image.

[jleveque]

@nikos-github: FYI, sonic-buildimage submodule update containing #405 in PR here: sonic-net/sonic-buildimage#2376