[show][muxcable] Catch port Value error exception (#2076) (#2486)

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#### What I did
Catch the exception if a user passes in an invalid port name.

#### How I did it
Added a try/catch to catch the ValueError.

#### How to verify it
Run "show muxcable cableinfo [invalid port]".

#### Previous command output (if the output of a command-line utility has changed)
```
crystalnet@ibr01:~$ show muxcable cableinfo all
Traceback (most recent call last):
  File "/usr/local/bin/show", line 8, in <module>
    sys.exit(cli())
  File "/usr/local/lib/python3.7/dist-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.7/dist-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.7/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.7/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.7/dist-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.7/dist-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python3.7/dist-packages/click/decorators.py", line 64, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "/usr/local/lib/python3.7/dist-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python3.7/dist-packages/show/muxcable.py", line 626, in cableinfo
    physical_port_list = platform_sfputil_helper.logical_port_name_to_physical_port_list(port)
  File "/usr/local/lib/python3.7/dist-packages/utilities_common/platform_sfputil_helper.py", line 53, in logical_port_name_to_physical_port_list
    return [int(port_name)]
ValueError: invalid literal for int() with base 10: 'all'
crystalnet@ibr01:~$
```

#### New command output (if the output of a command-line utility has changed)
```
crystalnet@ibr01:~$ show muxcable cableinfo all
Invalid port 'all'
ERR: Unable to get a port on muxcable port
crystalnet@ibr01:~$ 
```

tests/muxcable_test.py

@@ -384,6 +384,11 @@
 Credo     CACL1X321P2PA1M
 """
 
+expected_muxcable_cableinfo_invalid_port_output = """\
+Invalid port 'abc'
+ERR: Unable to get a port on muxcable port
+"""
+
 show_muxcable_hwmode_muxdirection_active_expected_output = """\
 Port        Direction    Presence
 ----------  -----------  ----------
@@ -1169,6 +1174,21 @@ def test_show_muxcable_cableinfo_incorrect_logical_port_return_value(self):
                                ["Ethernet0"], obj=db)
         assert result.exit_code == 1
 
+    @mock.patch('sonic_y_cable.y_cable.get_part_number', mock.MagicMock(return_value=(False)))
+    @mock.patch('sonic_y_cable.y_cable.get_vendor', mock.MagicMock(return_value=(False)))
+    @mock.patch('show.muxcable.platform_sfputil', mock.MagicMock(return_value=1))
+    def test_show_muxcable_cableinfo_invalid_port(self):
+        runner = CliRunner()
+        db = Db()
+
+        result = runner.invoke(show.cli.commands["muxcable"].commands["cableinfo"],
+                               ["Ethernet0"], obj=db)
+        assert result.exit_code == 1
+
+        result = runner.invoke(show.cli.commands["muxcable"].commands["cableinfo"],
+                               ["abc"], obj=db)
+        assert result.exit_code == 1
+        assert result.output == expected_muxcable_cableinfo_invalid_port_output
 
     @mock.patch('show.muxcable.delete_all_keys_in_db_table', mock.MagicMock(return_value=0))
     @mock.patch('show.muxcable.update_and_get_response_for_xcvr_cmd', mock.MagicMock(return_value={0: 0,

utilities_common/platform_sfputil_helper.py

@@ -53,14 +53,17 @@ def platform_sfputil_read_porttab_mappings():
 
 
 def logical_port_name_to_physical_port_list(port_name):
-    if port_name.startswith("Ethernet"):
-        if platform_sfputil.is_logical_port(port_name):
-            return platform_sfputil.get_logical_to_physical(port_name)
+    try:
+        if port_name.startswith("Ethernet"):
+            if platform_sfputil.is_logical_port(port_name):
+                return platform_sfputil.get_logical_to_physical(port_name)
         else:
-            click.echo("Invalid port '{}'".format(port_name))
-            return None
-    else:
-        return [int(port_name)]
+            return [int(port_name)]
+    except ValueError:
+        pass
+
+    click.echo("Invalid port '{}'".format(port_name))
+    return None
 
 
 def get_logical_list():