Keep pagure working on older version of flask not having iter_blueprints
    
    This function has been added after 0.10 and is thus not available in
    EPEL7 at this time.
    This commit makes pagure compatible with this version of flask by
    replacing the call to iter_blueprints() by using the attribute
    .blueprints which is a dict of all the blueprints of the application.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>