Bad ICU dependency handling

在类似 RH 的系统上重现 ICU 失败，然后从 mssqlcli/mssql_cli.py 和 mssqlcli/mssqlcliclient.py 开始，跟踪连接请求经过 jsonrpc/contracts/request.py 和 connectionservice.py 的流程。检查进程失败及由此产生的 AttributeError 是如何报告的；当用户收到清晰、可操作的 ICU 依赖错误，且没有次级 traceback 时，即表示完成。

When running on a RH-like system, I run into:

Couldn't find a valid ICU package installed on the system. Set the configuration flag System.Globalization.Invariant to true if you want to run with no globalization support.

   at System.Environment.FailFast(System.String)
   at System.Globalization.GlobalizationMode.GetGlobalizationInvariantMode()
   at System.Globalization.GlobalizationMode..cctor()
   at System.Globalization.CultureData.CreateCultureWithInvariantData()
   at System.Globalization.CultureData.get_Invariant()
   at System.Globalization.CultureInfo..cctor()
   at System.StringComparer..cctor()
   at System.AppDomain.InitializeCompatibilityFlags()
   at System.AppDomain.Setup(System.Object)
Traceback (most recent call last):
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/jsonrpc/contracts/request.py", line 51, in get_response
    response = self.json_rpc_client.get_response(self.request_id, self.owner_uri)
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/jsonrpc/jsonrpcclient.py", line 84, in get_response
    raise self.exception_queue.get()
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/jsonrpc/jsonrpcclient.py", line 124, in _listen_for_response
    response = self.reader.read_response()
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/jsonrpc/jsonrpcclient.py", line 272, in read_response
    while (not self.needs_more_data or self.read_next_chunk()):
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/jsonrpc/jsonrpcclient.py", line 326, in read_next_chunk
    raise EOFError(u'End of stream reached, no output.')
EOFError: End of stream reached, no output.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib64/python3.9/runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib64/python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/main.py", line 122, in <module>
    main()
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/main.py", line 115, in main
    run_cli_with(mssqlcli_options)
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/main.py", line 52, in run_cli_with
    mssqlcli.connect_to_database()
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/mssql_cli.py", line 278, in connect_to_database
    owner_uri, error_messages = self.mssqlcliclient_main.connect_to_database()
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/mssqlcliclient.py", line 91, in connect_to_database
    owner_uri, error_messages = self._execute_connection_request_with(connection_params)
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/mssqlcliclient.py", line 180, in _execute_connection_request_with
    response = connection_request.get_response()
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/jsonrpc/contracts/request.py", line 67, in get_response
    return self.response_error(error)
  File "/home/viraptor/dbcli/lib64/python3.9/site-packages/mssqlcli/jsonrpc/contracts/connectionservice.py", line 22, in response_error
    u'ownerUri': cls.owner_uri,
AttributeError: type object 'ConnectionRequest' has no attribute 'owner_uri'

I would expect some better/actionable error here.