Update to match redis 6.0.6+ handling exec failures

They now map plain errors into EXECABORT. This should keep Travis happy
again.

README.rst

@@ -96,7 +96,7 @@ your error handling. Simply set the connected attribute of the server to
 
 Fakeredis implements the same interface as `redis-py`_, the
 popular redis client for python, and models the responses
-of redis 5.0.
+of redis 6.0 (although most new feature in 6.0 are not supported).
 
 Support for aioredis
 ====================

fakeredis/_server.py

@@ -815,6 +815,7 @@ def sendall(self, data):
     def _process_command(self, fields):
         if not fields:
             return
+        func_name = None
         try:
             func, func_name = self._name_to_func(fields[0])
             sig = func._fakeredis_sig
@@ -835,6 +836,8 @@ def _process_command(self, fields):
                 # TODO: should not apply if the exception is from _run_command
                 # e.g. watch inside multi
                 self._transaction_failed = True
+            if func_name == 'exec' and exc.value.startswith('ERR '):
+                exc.value = 'EXECABORT Transaction discarded because of: ' + exc.value[4:]
             result = exc
         result = self._decode_result(result)
         if not isinstance(result, NoResponse):

test/test_fakeredis.py

@@ -3382,6 +3382,14 @@ def test_pipeline_move(r):
         p.execute()
 
 
+@pytest.mark.min_server('6.0.6')
+def test_exec_bad_arguments(r):
+    # Redis 6.0.6 changed the behaviour of exec so that it always fails with
+    # EXECABORT, even when it's just bad syntax.
+    with pytest.raises(redis.exceptions.ExecAbortError):
+        r.execute_command('exec', 'blahblah')
+
+
 def test_key_patterns(r):
     r.mset({'one': 1, 'two': 2, 'three': 3, 'four': 4})
     assert sorted(r.keys('*o*')) == [b'four', b'one', b'two']