Update dal.py

I was running my application and got this error

{
<type 'exceptions.ImportError'> cannot import name Set

Version
web2py™	Version 2.10.4-stable+timestamp.2015.04.26.15.11.54
Python	Python 2.7.3: /usr/bin/python (prefix: /usr)
Traceback
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Traceback (most recent call last):
  File "/home/www-data/web2py/gluon/restricted.py", line 227, in restricted
    exec ccode in environment
  File "/home/www-data/web2py/applications/omniavx_cxn/controllers/valuecache.py", line 6897, in <module>
  File "/home/www-data/web2py/gluon/globals.py", line 393, in <lambda>
    self._caller = lambda f: f()
  File "/home/www-data/web2py/applications/omniavx_cxn/controllers/valuecache.py", line 6584, in browse_bacct_callback
    from plugin_PowerGrid.CallBack import CallBack
  File "/home/www-data/web2py/gluon/custom_import.py", line 95, in custom_importer
    return base_importer(pname, globals, locals, fromlist, level)
  File "/home/www-data/web2py/gluon/custom_import.py", line 134, in __call__
    result = NATIVE_IMPORTER(name, globals, locals, fromlist, level)
  File "applications/omniavx_cxn/modules/plugin_PowerGrid/CallBack.py", line 41, in <module>
    from gluon.dal import Table ,Query, Set, Rows, Row
ImportError: cannot import name Set
}

same code produced no error in earlier version of web2py



line 15 of web2py/gluon/dal.py is 
{
from pydal.objects import Row, Rows, Table, Query, Expression
}

replacing that with 
{
from pydal.objects import Row, Rows, Table, Query, Set, Expression

}

solves the problem

gluon/dal.py

@@ -12,7 +12,7 @@ Takes care of adapting pyDAL to web2py's needs
 
 from pydal import DAL as DAL
 from pydal import Field
-from pydal.objects import Row, Rows, Table, Query, Expression
+from pydal.objects import Row, Rows, Table, Query, Set, Expression
 from pydal import SQLCustomType, geoPoint, geoLine, geoPolygon