Add pickle version as part of clcache version

This way we make sure that we unpickle only objects with a supported
pickle format version.

pyraf/clcache.py

@@ -48,7 +48,8 @@
 
 
 def _currentVersion():
-    return "4e" if pyrafglobals._use_ecl else "4c"
+    v = "4e" if pyrafglobals._use_ecl else "4c"
+    return v + str(sqliteshelve.pickle_version)
 
 
 class _FileContentsCache(filecache.FileCacheDict):

pyraf/sqliteshelve.py

@@ -27,6 +27,10 @@
 import os
 
 
+pickle_protocol = 4
+"""Protocol version to use for pickling objects"""
+
+
 class Shelf:
     """An SQLite implementation of the Python Shelf interface
 
@@ -75,7 +79,7 @@ def __setitem__(self, key, value):
         """
         if self.readonly:
             raise OSError("Readonly database")
-        pdata = pickle.dumps(value, protocol=4)
+        pdata = pickle.dumps(value, protocol=pickle_protocol)
         cursor = self.db.cursor()
         try:
             cursor.execute("insert or replace into shelf (key_str, value_str)"