generate_beacon_file.py: exit if input file is missing (after sending email)
generate_beacon_file.py: exit if input file is missing (after sending email)

ubtue/ub_tools,ubtue/ub_tools,ubtue/ub_tools,ubtue/ub_tools,ubtue/ub_tools,ubtue/ub_tools,ubtue/ub_tools,ubtue/ub_tools