cron_ipmi_sensors.py: TypeError: write() argument must be str, not bytes

[Joe Guo]

After `juju upgrade-charm --switch cs:hw-health-0 hw-health`, I found following exception:

/usr/local/lib/nagios/plugins/cron_ipmi_sensors.py --noentityabsent
    Traceback (most recent call last):
    File "/usr/local/lib/nagios/plugins/cron_ipmi_sensors.py", line 61, in <module>
        gather_metrics()
    File "/usr/local/lib/nagios/plugins/cron_ipmi_sensors.py", line 50, in gather_metrics
        fd.write(output)
    TypeError: write() argument must be str, not bytes

[Joe Guo (guoqiao)]

In py2: open with `w` == `wb`
In py3: `w` == `wt`
However, subprocess.check_output always return bytes, in both py2/py3.
So in py3, while trying to write output (bytes) to file opened with `w` (`wt`, expect text), it will raise error.

Merge created to fix this bug.

[Alvaro Uria (aluria)]

Released at cs:~llama-charmers-next/hw-health-2

Please confirm the fix and we will backport it to stable/20.05.

[Márton Kiss (marton-kiss)]

I can confirm it is not throwing the exception anymore with the cs:~llama-charmers-next/hw-health-2 charm.

[Andrea Ieri (aieri)]

The fix has been backported to cs:hw-health-2 (20.05)