Python: Port getCyclomaticComplexity function

Author: tausbn

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowDispatch.qll

@@ -2369,6 +2369,19 @@ module Reachability {
     )
   }
 
+  /**
+   * Holds if `node` is unlikely to raise an exception. This includes entry nodes
+   * and simple name lookups.
+   */
+  private predicate unlikelyToRaise(ControlFlowNode node) {
+    exists(node.getAnExceptionalSuccessor()) and
+    (
+      node.getNode() instanceof Name
+      or
+      exists(Scope s | s.getEntryNode() = node)
+    )
+  }
+
   /**
    * Holds if it is highly unlikely for control to flow from `node` to `succ`.
    */
@@ -2381,6 +2394,10 @@ module Reachability {
     succ = node.getASuccessor() and
     not succ = node.getAnExceptionalSuccessor() and
     not succ.getNode() instanceof Yield
+    or
+    // Exception edge from a node that is unlikely to raise
+    unlikelyToRaise(node) and
+    succ = node.getAnExceptionalSuccessor()
   }
 
   private predicate startBbLikelyReachable(BasicBlock b) {