Fix Handle non-responsive SFP modules gracefully in sfputil

[nhilderm-ciena]

Handle non-responsive SFP modules gracefully in sfputil show eeprom and show fwversion commands.

What I did

Added None guards in sfputil show eeprom and show fwversion commands to prevent crashes when transceiver modules are non-responsive or return None from platform API calls.

When an SFP module is physically present but non-responsive (e.g. due to I2C timeout), the platform API calls get_transceiver_info() and get_xcvr_api() return None. The existing code does not check for None before attempting to use the return values, causing unhandled exceptions.

The Problem:

• In sfputil show eeprom, get_transceiver_info() returns None for a non-responsive module but the code immediately passes the result to convert_sfp_info_to_output_string(), which crashes.
• In sfputil show fwversion, get_xcvr_api() returns None but the code immediately calls api.get_module_fw_info(), which crashes with AttributeError.

How I did it

Added explicit None checks:

• In eeprom command: check xcvr_info before processing, print error and continue to next port if None
• In fwversion command: check api before calling get_module_fw_info(), print error and exit gracefully if None

How to verify it

• Test with a non-responsive SFP module present:
  sfputil show eeprom -p EthernetX
  (should print error message instead of crashing)

• Test firmware version with non-responsive module:
  sfputil show fwversion -p EthernetX
  (should print error message instead of crashing)

• Test with responsive modules (regression):
  sfputil show eeprom
sfputil show fwversion -p EthernetX
  (should work normally)

Previous command output (if the output of a command-line utility has changed)

$ sfputil show eeprom -p Ethernet0
# (crashes with traceback when module is non-responsive)

New command output (if the output of a command-line utility has changed)

$ sfputil show eeprom -p Ethernet0
Ethernet0: SFP EEPROM detected
        Error: Failed to read EEPROM for this port

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: nhilderm-ciena / name: nhilderm (61f3823)

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[mssonicbld]

Hi, there are workflow run(s) waiting for approval, you may be first-time contributor. I will notify maintainers to help approve once PR is approved. Thanks!

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