Clarify timeout errors.

Specifically, not hiding the __cause__ of TimeoutError makes it visible
when it happens while connecting to a proxy.

Author: aaugustin

src/websockets/asyncio/client.py

@@ -511,9 +511,9 @@ async def __await_impl__(self) -> ClientConnection:
                 else:
                     raise SecurityError(f"more than {MAX_REDIRECTS} redirects")
 
-        except TimeoutError:
+        except TimeoutError as exc:
             # Re-raise exception with an informative error message.
-            raise TimeoutError("timed out during handshake") from None
+            raise TimeoutError("timed out during opening handshake") from exc
 
     # ... = yield from connect(...) - remove when dropping Python < 3.10
 

src/websockets/sync/client.py

@@ -90,7 +90,7 @@ def handshake(
             self.protocol.send_request(self.request)
 
         if not self.response_rcvd.wait(timeout):
-            raise TimeoutError("timed out during handshake")
+            raise TimeoutError("timed out while waiting for handshake response")
 
         # self.protocol.handshake_exc is set when the connection is lost before
         # receiving a response, when the response cannot be parsed, or when the

src/websockets/sync/server.py

@@ -128,7 +128,7 @@ def handshake(
 
         """
         if not self.request_rcvd.wait(timeout):
-            raise TimeoutError("timed out during handshake")
+            raise TimeoutError("timed out while waiting for handshake request")
 
         if self.request is not None:
             with self.send_context(expected_state=CONNECTING):

tests/asyncio/test_client.py

@@ -396,7 +396,7 @@ async def test_timeout_during_handshake(self):
                     self.fail("did not raise")
             self.assertEqual(
                 str(raised.exception),
-                "timed out during handshake",
+                "timed out during opening handshake",
             )
 
     async def test_connection_closed_during_handshake(self):
@@ -641,7 +641,7 @@ async def test_socks_proxy_connection_timeout(self):
                         self.fail("did not raise")
         self.assertEqual(
             str(raised.exception),
-            "timed out during handshake",
+            "timed out during opening handshake",
         )
         self.assertNumFlows(0)
 

tests/sync/test_client.py

@@ -164,7 +164,7 @@ def test_timeout_during_handshake(self):
                     self.fail("did not raise")
             self.assertEqual(
                 str(raised.exception),
-                "timed out during handshake",
+                "timed out while waiting for handshake response",
             )
 
     def test_connection_closed_during_handshake(self):