Python: Add BarrierGuard test with return inside unsafe branch

Author: RasmusWL

python/ql/test/experimental/dataflow/tainttracking/customSanitizer/TestTaint.expected

@@ -32,6 +32,7 @@ test_taint
 | test_logical.py:123 | ok   | test_nesting_not_with_and_true | s |
 | test_logical.py:126 | ok   | test_nesting_not_with_and_true | s |
 | test_logical.py:128 | ok   | test_nesting_not_with_and_true | s |
+| test_logical.py:137 | fail | test_with_return | s |
 isSanitizer
 | TestTaintTrackingConfiguration | test.py:21:39:21:39 | ControlFlowNode for s |
 | TestTaintTrackingConfiguration | test.py:50:10:50:29 | ControlFlowNode for emulated_escaping() |

python/ql/test/experimental/dataflow/tainttracking/customSanitizer/test_logical.py

@@ -128,6 +128,15 @@ def test_nesting_not_with_and_true():
         ensure_not_tainted(s)
 
 
+def test_with_return():
+    s = TAINTED_STRING
+
+    if not is_safe(s):
+        return
+
+    ensure_not_tainted(s)
+
+
 # Make tests runable
 
 test_basic()
@@ -136,3 +145,4 @@ def test_nesting_not_with_and_true():
 test_tricky()
 test_nesting_not()
 test_nesting_not_with_and_true()
+test_with_return()