[client] Handle invalid proxy settings

[csordasmarton]

If HTTP_PROXY / HTTPS_PROXY environment variables are set and the
URL is invalid (e.g.: it doesn't contains a schema like localhost:8001)
the client will throw the following exception:

'NoneType' object has no attribute 'rfind'
  File "/codechecker/build/CodeChecker/cc_bin/CodeChecker.py", line 174, in <module>
    main(commands)
  File "/codechecker/build/CodeChecker/cc_bin/CodeChecker.py", line 141, in main
    sys.exit(args.func(args))
  File "//codechecker/build/CodeChecker/lib/python3/codechecker_client/cmd/store.py", line 856, in main
    traceback.print_stack()

From this error message it is hard to understand the real problem.

Unfortunately Thrift does not handle the use case when invalid proxy format
is used (e.g.: no schema is specified). For this reason we need to verify
the proxy format in our side.

[bruntib]

We should consider using a "local static"-ish variable instead of a global one:

def f():
  f.my_static_var = 42

[bruntib]

This function is not checking the http[s] scheme at the beginning, but line 73 says that it will be checked.
Minor thing: maybe the content of this function can go inside validate_proxy_format(), since it's quite short.

[csordasmarton]

@bruntib I created a new commit where I refactored the whole thing. I moved the checking under the BaseClientHelper class. This way we will handle the use case when no port number or invalid port number is set for the proxy environment variables.

[zomen2]

If THttpClient throws TTransportException for some reason but not because something bad with proxy settings then this finally branch try to validate proxy settings.
Please call self._validate_proxy_format() in the ValueError branch not in the finally branch.

[csordasmarton]

Only the THttpClient object creation is inside a try/except block, which cannot raise such exception like TTransportException.
Two scenarios are possible here:

• The user specified the following environment variable: HTTP_PROXY=http://localhost / HTTP_PROXY=http://localhost:not_a_number where the port is not specified or it is not an integer. In this case it will raise a ValueError exception.
• The user specified the following environment variable: HTTP_PROXY=localhost:8001 where the schema is not given. In this case the THttpClient object creation will not raise any exception (it will raise exception when an API call happens). So this is the reason when this object creation is done, we need to check the proxy format before any API call happens.

In both cases we need to check the proxy format. So it is not enough to call this function inside the ValueError branch. We need to call it every time when there is no exception.

Your comments are fixed.