Python: Don't re-export python under DataFlow::

Author: RasmusWL

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

@@ -1,9 +1,15 @@
 /**
  * Provides Python-specific definitions for use in the data flow library.
  */
+
+// we need to export `Unit` for the DataFlowImpl* files
+private import python as Python
+
 module Private {
   import DataFlowPrivate
+
   //   import DataFlowDispatch
+  class Unit = Python::Unit;
 }
 
 module Public {

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

@@ -2,6 +2,7 @@
  * Contains utility functions for writing data flow queries
  */
 
+private import python
 private import DataFlowPrivate
 import DataFlowPublic
 

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

@@ -6,7 +6,7 @@
  * local tracking within a function.
  */
 
-import python
+private import python
 import DataFlowPublic
 private import DataFlowPrivate
 private import semmle.python.internal.CachedStages

python/ql/test/experimental/dataflow/qll-private-imports/Test.expected

@@ -1 +1 @@
-| Add |
+ERROR: Could not resolve type DataFlow::Add (Test.ql:7,6-19)