Classify connection exceptions as operational errors to better conform with PEP 249

NEWS

@@ -1,6 +1,15 @@
 Current release
 ---------------
 
+What's new in psycopg 2.9.0
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Reclassified SQLSTATE connection exceptions (08XXX) as
+  `~psycopg2.errors.OperationalError`, conforming better to
+  PEP 249.  This error is a subclass of previously used
+  `~psycopg2.errors.DatabaseError`.
+
+
 What's new in psycopg 2.8.6
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

psycopg/error_type.c

@@ -65,6 +65,8 @@ base_exception_from_sqlstate(const char *sqlstate)
     switch (sqlstate[0]) {
     case '0':
         switch (sqlstate[1]) {
+        case '8': /* Class 08 - Connection Exception */
+            return OperationalError;
         case 'A': /* Class 0A - Feature Not Supported */
             return NotSupportedError;
         }

tests/test_errors.py

@@ -62,6 +62,13 @@ class ErrorsTests(ConnectingTestCase):
         with self.assertRaises(KeyError):
             errors.lookup('XXXXX')
 
+    def test_connection_exceptions_backwards_compatibility(self):
+        err = errors.lookup('08000')
+        # connection exceptions are classified as operational errors
+        self.assert_(issubclass(err, errors.OperationalError))
+        # previously these errors were classified only as DatabaseError
+        self.assert_(issubclass(err, errors.DatabaseError))
+
     def test_has_base_exceptions(self):
         excs = []
         for n in dir(psycopg2):