Fix load_session() and restrict loading a session in a different modu…

…le (#507)

* Don't update vars(main) twice

* Inspect the pickle beginnig to identify main and check against 'main' argument

* Save and restore modules created at runtime with ModuleType()

* tests: don't need to add runtime module to sys.modules

* load_session_copy(): load a session state into a runtime module

* tests: session tests code reorganization

* tests: test runtime created module session saving

* tests: test load_session_copy

* review: adjustments

* small fixes

* use __dict__

* naming changes

* review: final renaming and adjustments

dill/__init__.py

@@ -23,11 +23,13 @@
     del os, sys, parent, get_license_text, get_readme_as_rst
 
 
-from ._dill import dump, dumps, load, loads, dump_session, load_session, \
-    Pickler, Unpickler, register, copy, pickle, pickles, check, \
-    HIGHEST_PROTOCOL, DEFAULT_PROTOCOL, PicklingError, UnpicklingError, \
-    HANDLE_FMODE, CONTENTS_FMODE, FILE_FMODE, PickleError, PickleWarning, \
-    PicklingWarning, UnpicklingWarning
+from ._dill import (
+    dump, dumps, load, loads, dump_module, load_module, load_module_asdict,
+    dump_session, load_session, Pickler, Unpickler, register, copy, pickle,
+    pickles, check, HIGHEST_PROTOCOL, DEFAULT_PROTOCOL, PicklingError,
+    UnpicklingError, HANDLE_FMODE, CONTENTS_FMODE, FILE_FMODE, PickleError,
+    PickleWarning, PicklingWarning, UnpicklingWarning,
+)
 from . import source, temp, detect
 
 # get global settings