python: add example showing FP

Author: yoff

python/ql/test/query-tests/Variables/undefined/UninitializedLocal.expected

@@ -11,4 +11,5 @@
 | UninitializedLocal.py:163:7:163:7 | x | Local variable 'x' may be used before it is initialized. |
 | UninitializedLocal.py:176:16:176:16 | x | Local variable 'x' may be used before it is initialized. |
 | UninitializedLocal.py:178:16:178:16 | y | Local variable 'y' may be used before it is initialized. |
+| captured.py:8:15:8:17 | foo | Local variable 'foo' may be used before it is initialized. |
 | odasa3987.py:11:8:11:10 | var | Local variable 'var' may be used before it is initialized. |

python/ql/test/query-tests/Variables/undefined/captured.py

@@ -0,0 +1,14 @@
+#!/usr/bin/python
+
+def topLevel():
+    foo = 3
+
+    def bar():
+        nonlocal foo
+        print(foo)  # FP
+        foo = 4
+
+    bar()
+    print(foo)
+
+topLevel()