Fix the lambda issues.

test/normalizer_issue_files/E73.py

@@ -0,0 +1,16 @@
+#: E731:4
+f = lambda x: 2 * x
+while False:
+    #: E731:6
+    foo = lambda y, z: 2 * x
+# Okay
+f = object()
+f.method = lambda: 'Method'
+
+f = {}
+f['a'] = lambda x: x ** 2
+
+f = []
+f.append(lambda x: x ** 2)
+
+lambda: 'no-op'