Always raise OperationalError when connection was closed externally.

From the DB-API (https://www.python.org/dev/peps/pep-0249/):

  OperationalError

  Exception raised for errors that are related to the database's
  operation and not necessarily under the control of the programmer,
  e.g. an unexpected disconnect occurs, [...]

Additionally, psycopg2 was inconsistent, at least in the async case:
depending on how the "connection closed" error was reported from the
kernel to libpq, it would sometimes raise OperationalError and
sometimes DatabaseError. Now it always raises OperationalError.

2 files changed, 7 insertions, 5 deletions

diff --git a/psycopg/pqpath.c b/psycopg/pqpath.c
index 222696b..f270ce8 100644
--- a/psycopg/pqpath.c
+++ b/psycopg/pqpath.c
@@ -179,8 +179,10 @@ pq_raise(connectionObject *conn, cursorObject *curs, PGresult **pgres)
 
     /* if the connection has somehow been broken, we mark the connection
        object as closed but requiring cleanup */
-    if (conn->pgconn != NULL && PQstatus(conn->pgconn) == CONNECTION_BAD)
+    if (conn->pgconn != NULL && PQstatus(conn->pgconn) == CONNECTION_BAD) {
         conn->closed = 2;
+        exc = OperationalError;
+    }
 
     if (pgres == NULL && curs != NULL)
         pgres = &curs->pgres;
@@ -214,9 +216,9 @@ pq_raise(connectionObject *conn, cursorObject *curs, PGresult **pgres)
     if (code != NULL) {
         exc = exception_from_sqlstate(code);
     }
-    else {
-        /* Fallback if there is no exception code (reported happening e.g.
-         * when the connection is closed). */
+    else if (exc == NULL) {
+        /* Fallback if there is no exception code (unless we already
+           determined that the connection was closed). */
         exc = DatabaseError;
     }
 
diff --git a/tests/test_cursor.py b/tests/test_cursor.py
index f9fc66c..98891ea 100755
--- a/tests/test_cursor.py
+++ b/tests/test_cursor.py
@@ -575,7 +575,7 @@ class CursorTests(ConnectingTestCase):
                 cur.execute('select pg_terminate_backend(%s)', (pid1,))
 
             time.sleep(0.001)
-            with self.assertRaises(psycopg2.DatabaseError):
+            with self.assertRaises(psycopg2.OperationalError):
                 with victim_conn.cursor() as cur:
                     cur.execute('select 1')
                     wait_func(victim_conn)