Exception due to double-resolution of values with Enums in pagination

[dilbernd]

I have an enum value in a table:

class AddressFamily(enum.Enum):
    IPv4 = 4
    IPv6 = 6

    Column('address_family', Enum(AddressFamily)),

When I paginate a core query, sqlakeyset removes some columns in paging.py:

        N = len(row._row) - len(extra_columns)
        row = row[:N]

__getitem__ on BaseRowProxy however applies processing to the values, which resolves the enum from its string name to the actual enum value:

                            l.append(processor(value))

When I then try to read the value from the row I received out of pagination:

row[prefixes.c.address_family]

Here, the value gets resolved again, using the str() of the already resolved enum as a lookup key, and I get an exception: 'AddressFamily.IPv4' is not among the defined enum values. Enum name: addressfamily. Possible values: IPv4, IPv6

[acarapetis]

Thanks for your thorough bug report! I'm super busy at the moment, but I'll try to fix this soon; in the mean time, PRs are welcome! Should just be a matter of accessing the guts of BaseRowProxy rather than using its public getitemn when we trim off the extra columns.