pylxd/client: guard against cert=None

[simondeziel]

>>> import pylxd
>>> c = pylxd.Client(endpoint="https://127.0.0.1:8443/", cert=None,  verify=False)
/opt/pylxd/.tox/integration/lib/python3.12/site-packages/urllib3/connectionpool.py:1099: InsecureRequestWarning: Unverified HTTPS request is being made to host '127.0.0.1'. Adding certificate verification is strongly advised. See: https://urllib3.readthedocs.io/en/latest/advanced-usage.html#tls-warnings
  warnings.warn(
>>> c.authenticate("password")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/pylxd/.tox/integration/lib/python3.12/site-packages/pylxd/client.py", line 573, in authenticate
    cert = open(self.api.session.cert[0]).read().encode("utf-8")
                ~~~~~~~~~~~~~~~~~~~~~^^^
TypeError: 'NoneType' object is not subscriptable

[simondeziel]

@hamistao while touching that part of the code, I noticed that Certificates.create() is badly named as it doesn't create any cert but "onboard" an existing certificate on the LXD remote by mean of a token or a password.

[hamistao]

@hamistao while touching that part of the code, I noticed that Certificates.create() is badly named as it doesn't create any cert but "onboard" an existing certificate on the LXD remote by mean of a token or a password.

I noticed the same thing, but I don't think we can do anything about it besides maybe putting a comment to explain what the funciton does.

[hamistao]

If the purpose is just to check if the file exists, just open(self.api.session.cert[0]) should suffice.
Also, I think we should close the file in case it exists.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 95.38%. Comparing base (de04a29) to head (e4ba9b9).
Report is 53 commits behind head on main.

Files with missing lines	Patch %	Lines
pylxd/client.py	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #618      +/-   ##
==========================================
- Coverage   96.24%   95.38%   -0.86%     
==========================================
  Files          32       32              
  Lines        3165     3229      +64     
==========================================
+ Hits         3046     3080      +34     
- Misses        119      149      +30     

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[hamistao]

Sorry for the sudden review, but this looks good to me!