Cannot install rabbitmq management tool
I just ran into this exact same error message when I enabled the rabbitmq_tracing plugin on Fedora21. Short story: you should be fine. RabbitMQ started right up for me with this plugin enabled (and all its dependent plugins including rabbitmq_management and Mochiweb)

I think there may be a problem with how RabbitMQ is detecting Erlang versions? From looking at http://www.erlang.org/documentation/ it appears that:


Release R13B01 maps to version 5.7.2 
Release 17 maps to versions 6.x


So by running Erlang release 17 we appear to be running a sufficiently recent version to work with the Mochiweb plugin.