Don't try to translate aiosfstream exceptions

The translate_errors_context context manager, which is responsible
for translating aiocometd exceptions to their aiosfstream
counterparts, caught aiosfstream exceptions as well and tried to
translate them, resulting in a KeyError.
Catch the aiosfstream exceptions and let them pass through before
aiocometd exception types are considered.

aiosfstream/exceptions.py

@@ -106,6 +106,8 @@ def translate_errors_context():
     """
     try:
         yield
+    except AiosfstreamException:
+        raise
     except cometd_exc.AiocometdException as cometd_error:
         error_cls = EXCEPTION_PAIRS[type(cometd_error)]
         raise error_cls(*cometd_error.args) from cometd_error

tests/test_exceptions.py

@@ -118,3 +118,31 @@ async def raise_error():
             await exc.translate_errors(raise_error)()
 
         self.assertEqual(cm.exception.args, error.args)
+
+    def test_reraises_sfstream_error(self):
+        response = {
+            "error": "400:arg1,arg2:description"
+        }
+        error = exc.ServerError("Message", response)
+
+        def raise_error():
+            raise error
+
+        with self.assertRaises(exc.ServerError) as cm:
+            exc.translate_errors(raise_error)()
+
+        self.assertEqual(cm.exception.args, error.args)
+
+    async def test_async_reraises_sfstream_error(self):
+        response = {
+            "error": "400:arg1,arg2:description"
+        }
+        error = exc.ServerError("Message", response)
+
+        async def raise_error():
+            raise error
+
+        with self.assertRaises(exc.ServerError) as cm:
+            await exc.translate_errors(raise_error)()
+
+        self.assertEqual(cm.exception.args, error.args)