sage.misc.persist: Make import for SAGE_DB local to functions

Author: Matthias Koeppe

src/sage/misc/persist.pyx

@@ -40,7 +40,6 @@ from textwrap import dedent
 import zlib; comp = zlib
 import bz2; comp_other = bz2
 
-from .misc import SAGE_DB
 from .sage_unittest import TestSuite
 
 
@@ -1124,6 +1123,7 @@ def db(name):
 
     The database directory is ``$HOME/.sage/db``.
     """
+    from .misc import SAGE_DB
     return load('%s/%s'%(SAGE_DB,name))
 
 
@@ -1136,4 +1136,5 @@ def db_save(x, name=None):
     try:
         x.db(name)
     except AttributeError:
+        from .misc import SAGE_DB
         save(x, '%s/%s'%(SAGE_DB,name))