Add test for FP for py/should-use-with

Author: owen-mc

python/ql/test/query-tests/Statements/general/ShouldUseWithStatement.expected

@@ -1 +1,2 @@
 | test.py:168:9:168:17 | Attribute() | Instance of context-manager class $@ is closed in a finally block. Consider using 'with' statement. | test.py:151:1:151:17 | Class CM | CM |
+| test.py:182:13:182:26 | Attribute() | Instance of context-manager class $@ is closed in a finally block. Consider using 'with' statement. | test.py:151:1:151:17 | Class CM | CM |

python/ql/test/query-tests/Statements/general/test.py

@@ -167,6 +167,20 @@ def no_with():
     finally:
         f.close()
 
+# Should use context manager, with the resource held in an instance attribute
+# (caught via instance-attribute type tracking).
+class HoldsCM(object):
+
+    def __init__(self):
+        self.f = CM()
+
+    def no_with_attribute(self):
+        try:
+            self.f.write("Hello ")
+            self.f.write(" World\n")
+        finally:
+            self.f.close()
+
 #Assert without side-effect
 def assert_ok(seq):
     assert all(isinstance(element, (str, unicode)) for element in seq)