Client: Warn user about using bad credentials

[YouSafe]

Using the wrong password leads to a rather confusing error message (see below). A warning that the post request returned with "Bad Credentials" would help in this situation.

OpenBench/Client/worker.py

Lines 922 to 928 in 9906bad

	data = requests.post(target, data=payload, timeout=TIMEOUT_HTTP).json()
	# Might already have a sufficiently new Fastchess binary
	print ('> Checking for existing %s-ob binary' % name)
	runner_path = os.path.join(os.getcwd(), '%s-ob' % name)
	runner_path = utils.check_for_engine_binary(runner_path)
	acceptable_ver = compare_versions(runner_path, data['%s_min_version' % name])

Looking for Make... [v4.3]
Looking for C++ Compiler... [g++ v13.3.0]
Looking for Syzygy... [0-Man]

Configuring fastchess...
> Requesting fastchess configuration from openbench
> Checking for existing fastchess-ob binary


[Note] Unable to locate and/or build desired Fastchess version!
[Note] Sleeping for 15 seconds
[Note] Traceback:
Traceback (most recent call last):
  File "/home/openbench/OpenBench/Client/client.py", line 48, in try_forever
    return func(*args)
           ^^^^^^^^^^^
  File "/home/openbench/OpenBench/Client/worker.py", line 913, in server_configure_fastchess
    server_configure_match_runner(config, 'fastchess', build_fastchess_in_dir)
  File "/home/openbench/OpenBench/Client/worker.py", line 928, in server_configure_match_runner
    acceptable_ver = compare_versions(runner_path, data['%s_min_version' % name])
                                                   ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: 'fastchess_min_version'