There's an unbound local error in activate_task.py as indicated by https://parsley.corp.mongodb.com/evergreen/mongodb_mongo_master_linux_x86_dynamic_debug_wtdevelop_compile_archive_dist_test_0d064cacbc975e8c78f32c10f3cfc5a5f6d192b4_26_03_03_05_28_12/0/task?bookmarks=0,2457.

It looks like if there's a failure to find the appropriate task, we see an unbound_local error in the else block since build_variant is not set