Show low-level OS error on TCP connection errors.

src/smbprotocol/transport.py

@@ -65,7 +65,7 @@ def connect(self):
                 try:
                     self._sock = socket.create_connection((self.server, self.port), timeout=self.timeout)
                 except (OSError, socket.gaierror) as err:
-                    raise ValueError(f"Failed to connect to '{self.server}:{self.port}'") from err
+                    raise ValueError(f"Failed to connect to '{self.server}:{self.port}': {err}") from err
                 self._sock.settimeout(None)  # Make sure the socket is in blocking mode.
                 self.connected = True
 

tests/test_transport.py

@@ -72,8 +72,15 @@ def test_normal_fail_message_too_big(self):
         )
 
     def test_invalid_host(self):
+        """
+        Raises ValueError when failing to connect to the remote server.
+
+        The error message contains the low-level OS error details.
+        """
         tcp = Tcp("fake-host", 445)
-        with pytest.raises(ValueError, match=re.escape("Failed to connect to 'fake-host:445'")):
+        # We just check for OSError marker, as the actual error message
+        # might be different based on current OS.
+        with pytest.raises(ValueError, match=r"Failed to connect to 'fake-host:445': \[Errno .*"):
             tcp.connect()