Credential Resolver Proposal

credentials.py

def create_credential_resolver(session):
    """Create a default credential resolver.

    This creates a pre-configured credential resolver
    that includes the default lookup chain for
    credentials.

    """
    profile_name = session.get_config_variable('profile') or 'default'
    credential_file = session.get_config_variable('credentials_file')
    config_file = session.get_config_variable('config_file')
    metadata_timeout = session.get_config_variable('metadata_service_timeout')
    num_attempts = session.get_config_variable('metadata_service_num_attempts')

    providers = [
        SharedCredentialProvider(
            creds_filename=credential_file,
            profile_name=profile_name
        ),
        # The new config file has precedence over the legacy
        # config file.
        ConfigProvider(config_filename=config_file, profile_name=profile_name),
        OriginalEC2Provider(),
        BotoProvider(),
        InstanceMetadataProvider(
            iam_role_fetcher=InstanceMetadataFetcher(
                timeout=metadata_timeout,
                num_attempts=num_attempts)
        )
    ]

    # We use ``session.profile`` for EnvProvider rather than
    # ``profile_name`` so that it can be ``None`` when unset.
    if session.profile is None:
        # No profile has been explicitly set, so we prepend the environment
        # variable provider.
        providers.insert(0, EnvProvider())
    else:
        logger.info('Skipping environment variable credential check'
                    ' because profile name was explicitly set.')

    resolver = CredentialResolver(providers=providers)
    return resolver