Don't crash when looking up a name in class scope after MRO error.

Fixes #2001.

mypy/semanal.py

@@ -2247,7 +2247,7 @@ def lookup(self, name: str, ctx: Context) -> SymbolTableNode:
                 return None
         # 2. Class attributes (if within class definition)
         if self.is_class_scope() and name in self.type.names:
-            return self.type[name]
+            return self.type.names[name]
         # 3. Local (function) scopes
         for table in reversed(self.locals):
             if table is not None and name in table:

test-data/unit/check-classes.test

@@ -2059,3 +2059,9 @@ class B(A): pass
 class C(B): pass
 class D(A, B): pass # E: Cannot determine consistent method resolution order (MRO) for "D"
 class E(C, D): pass # E: Cannot determine consistent method resolution order (MRO) for "E"
+
+[case testInconsistentMroLocalRef]
+class A: pass
+class B(object, A): # E: Cannot determine consistent method resolution order (MRO) for "B"
+    def readlines(self): pass
+    __iter__ = readlines