[ssh] Decoding the output of the sysupgrade command fails with UnicodeDecodeError

[okraits]

I did a firmware upgrade with openwisp-firmware-upgrader. It was successful, but I got the following exception twice:

Traceback (most recent call last):
  File "/home/okraitschy/owm_new/build/venv/lib/python3.7/site-packages/billiard/process.py", line 327, in _bootstrap        
    self.run()                                         
  File "/home/okraitschy/owm_new/build/venv/lib/python3.7/site-packages/billiard/process.py", line 114, in run                
    self._target(*self._args, **self._kwargs)
  File "/home/okraitschy/owm_new/build/venv/lib/python3.7/site-packages/openwisp_firmware_upgrader/upgraders/openwrt.py", line
 134, in upgrade                                                                                                             
    conn.exec_command(command, timeout=timeout)                                                                              
  File "/home/okraitschy/owm_new/build/venv/lib/python3.7/site-packages/openwisp_controller/connection/connectors/ssh.py", line 136, in exec_command
    output = output_str.decode('utf8').strip()  
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xc3 in position 6586: invalid continuation byte

Due to sysupgrade -v, the verbose output of sysupgrade is decoded and that fails because of some byte.

https://github.com/openwisp/openwisp-controller/blob/master/openwisp_controller/connection/connectors/ssh.py#L136

Just some thoughts:

Why do we print out the output?
Why do we decode it?
Why don't we catch exceptions there?

[nemesifier]

@okraits:

Why do we print out the output?

if I remember correctly, print is used for logging and could be changed to logger.info()

Why do we decode it?

I don't remember now, it may be that the returned value is byte. Not sure.

Why don't we catch exceptions there?

I didn't account for this failure.

[okraits]

if I remember correctly, print is used for logging and could be changed to logger.info()

Yeah, I was also thinking about converting this to logging.

I don't remember now, it may be that the returned value is byte. Not sure.

I will have a look into it.

I didn't account for this failure.

I didn't mean that as an accusation. Thank you for your great work!

I'll try to come up with a PR for this.