Git ssh key issues not reported

[ben-edna]

Given a project at git@github.com:dfetch-org/dfetch
When i run dfetch -v check
Then in case of an ssh key issue, no output is given to find the reason why

There is a part that tries to determine the VCS type by doing git ls-remote --heads, but even with more verbosity it doesn't output any additional info.

[spoorcc]

Could see If using asyncssh would make it possible to test ssh repo's locally in a cross platform way:

@given("it is accessible over SSH")
def step_start_ssh(context):
    import asyncssh, asyncio, os
    repo_dir = context.repo_dir

    loop = asyncio.new_event_loop()
    asyncio.set_event_loop(loop)

    host_key_file = os.path.join(repo_dir, "ssh_host_key")
    asyncssh.generate_private_key("ssh-rsa").write_private_key_file(host_key_file)

    class GitSSHServer(asyncssh.SSHServer):
        pass

    class GitSSHSession(asyncssh.SSHServerSession):
        def __init__(self):
            self._process = None

        def exec_requested(self, command):
            if command.startswith("git-upload-pack") or command.startswith("git-receive-pack"):
                self._process = subprocess.Popen(
                    command.split(),
                    stdin=subprocess.PIPE,
                    stdout=subprocess.PIPE,
                    stderr=subprocess.PIPE,
                    cwd=repo_dir
                )
                return True
            return False

        def stdin_received(self, data, datatype):
            if self._process:
                self._process.stdin.write(data)
            return len(data)

        def eof_received(self):
            if self._process:
                self._process.stdin.close()
            return False

        def session_ended(self):
            if self._process:
                self._process.wait()

    server = loop.run_until_complete(
        asyncssh.listen(
            '', 0,
            server_host_keys=[host_key_file],
            server_factory=GitSSHServer,
            username="gituser",
            password="password123",
            session_factory=GitSSHSession
        )
    )

    context.ssh_port = server.get_port()
    context.ssh_server = server
    context.ssh_loop = loop

[spoorcc]

Maybe the BatchMode=yes for the #570 fix in #908 also improves this