Can't handle duplicate column names in sql read
Possibly related to #3468 

Using pandas 0.10.1.
It's legal for sql (at least Sql Server) to have queries that return two columns with the same name. And it's legal for pandas to have dataframes that have two columns with the same name. But pandas gives a very misleading error message when you try it with read_frame:
# Query that has 2 columns with the same name:

sql = "select 1 as whatever, 2 as name, 3 as name where 1=0"
pos = pandas.io.sql.read_frame(sql, dbconn)
# That gives very misleading error message
