[PR #12136/c0f1513c backport][3.13] Fix AttributeError: 'ClientConnectorCertificateError' object has no attribute '_os_error'. (#12147)

**This is a backport of PR #12136 as merged into master
(c0f1513).**

Co-authored-by: themylogin <themylogin@gmail.com>

Author: patchback[bot]

CHANGES/12136.bugfix.rst

@@ -0,0 +1,2 @@
+``ClientConnectorCertificateError.os_error`` no longer raises :exc:`AttributeError`
+-- by :user:`themylogin`.

CONTRIBUTORS.txt

@@ -378,6 +378,7 @@ Vladimir Kamarzin
 Vladimir Kozlovski
 Vladimir Rutsky
 Vladimir Shulyak
+Vladimir Vinogradenko
 Vladimir Zakharov
 Vladyslav Bohaichuk
 Vladyslav Bondar

aiohttp/client_exceptions.py

@@ -386,10 +386,21 @@ class ClientConnectorSSLError(*ssl_error_bases):  # type: ignore[misc]
 class ClientConnectorCertificateError(*cert_errors_bases):  # type: ignore[misc]
     """Response certificate error."""
 
+    _conn_key: ConnectionKey
+
     def __init__(
-        self, connection_key: ConnectionKey, certificate_error: Exception
+        # TODO: If we require ssl in future, this can become ssl.CertificateError
+        self,
+        connection_key: ConnectionKey,
+        certificate_error: Exception,
     ) -> None:
-        self._conn_key = connection_key
+        if isinstance(certificate_error, cert_errors + (OSError,)):
+            # ssl.CertificateError has errno and strerror, so we should be fine
+            os_error = certificate_error
+        else:
+            os_error = OSError()
+
+        super().__init__(connection_key, os_error)
         self._certificate_error = certificate_error
         self.args = (connection_key, certificate_error)
 

tests/test_client_exceptions.py

@@ -232,6 +232,15 @@ def test_str(self) -> None:
             " [Exception: ('Bad certificate',)]"
         )
 
+    def test_oserror(self) -> None:
+        certificate_error = OSError(1, "Bad certificate")
+        err = client.ClientConnectorCertificateError(
+            connection_key=self.connection_key, certificate_error=certificate_error
+        )
+        assert err.os_error == certificate_error
+        assert err.errno == 1
+        assert err.strerror == "Bad certificate"
+
 
 class TestServerDisconnectedError:
     def test_ctor(self) -> None: