Python: Add example if urlsplit(url).path: => missing points-to

I wanted to highlight that it's not the call to `urlsplit` that is a problem, so
that's why I inserted a `check` in-between.

python/ql/test/library-tests/PointsTo/regressions/missing/if-urlsplit-access/Test.expected

@@ -0,0 +1,3 @@
+| test.py:5:7:5:9 | ControlFlowNode for foo | int 42 |
+| test.py:11:11:11:13 | ControlFlowNode for foo | int 1 |
+| test.py:17:11:17:13 | ControlFlowNode for foo | <MISSING pointsTo()> |

python/ql/test/library-tests/PointsTo/regressions/missing/if-urlsplit-access/Test.ql

@@ -0,0 +1,10 @@
+import python
+
+from NameNode name, CallNode call, string debug
+where
+    call.getAnArg() = name and
+    call.getFunction().(NameNode).getId() = "check" and
+    if exists(name.pointsTo())
+    then debug = name.pointsTo().toString()
+    else debug = "<MISSING pointsTo()>"
+select name, debug

python/ql/test/library-tests/PointsTo/regressions/missing/if-urlsplit-access/options

@@ -0,0 +1 @@
+semmle-extractor-options: --max-import-depth=1 --lang=3

python/ql/test/library-tests/PointsTo/regressions/missing/if-urlsplit-access/test.py

@@ -0,0 +1,17 @@
+# Only a problem in Python 3
+from urllib.parse import urlsplit
+
+foo = 42
+check(foo)
+
+def func(url):
+    parts = urlsplit(url)
+
+    foo = 1
+    check(foo)
+
+    if parts.path: # using `urlsplit(url).path` here is equivalent
+        return # using `pass` here instead makes points-to work
+
+    foo = 2
+    check(foo) # no points-to information