S3 problem: profiles for assuming AWS roles do not appear to work (boto3 problem?)

I need to get data from a S3 bucket that requires me to assume a role.

I have configured my setup as [per aws instructions](http://docs.aws.amazon.com/cli/latest/userguide/cli-multiple-profiles.html) and have a profile called "dev". I then `export AWS_PROFILE=dev` and this works fine with the aws cli, asking for an MFA when required and caching the results in the .aws/cli/cache folder.

I assumed I could do this in my python program (in the same environment)
`odo('s3://some-bucket/data.csv', 'sqlite:database.db::data')`

And it would also use the profile. But it seems not to find it, as I get a
`boto.provider.ProfileNotFoundError: Profile "dev" not found!` on line 296 of boto/provider.py.

Reproduce the odo('s3://some-bucket/data.csv', 'sqlite:database.db::data') call with AWS_PROFILE=dev and compare it with the working AWS CLI setup. Start at boto/provider.py line 296 and trace how the profile is loaded, including the MFA cache; done means the configured profile is found and the S3-to-SQLite transfer no longer raises ProfileNotFoundError.

Written by the indexing model from the issue text.