The normal rabbitmq was started before. When it was started again today, an error was reported. The error message is as follows:

$ rabbitmq-server

              RabbitMQ 3.6.6. Copyright (C) 2007-2016 Pivotal Software, Inc.
  ##  ##      Licensed under the MPL.  See http://www.rabbitmq.com/
  ##  ##
  ##########  Logs: /Applications/Coding/rabbitmq/var/log/rabbitmq/[email protected]
  ######  ##        /Applications/Coding/rabbitmq/var/log/rabbitmq/[email protected]
  ##########
              Starting broker...


BOOT FAILED
===========

Error description:
   {could_not_start,rabbit,
       {undef,
           [{crypto,module_info,[attributes],[]},
            {rabbit_misc,module_attributes,1,
                [{file,"src/rabbit_misc.erl"},{line,798}]},
            {rabbit_misc,'-all_module_attributes/1-fun-0-',3,
                [{file,"src/rabbit_misc.erl"},{line,818}]},
            {lists,foldl,3,[{file,"lists.erl"},{line,1261}]},
            {rabbit_boot_steps,find_steps,1,
                [{file,"src/rabbit_boot_steps.erl"},{line,40}]},
            {rabbit_boot_steps,run_boot_steps,1,
                [{file,"src/rabbit_boot_steps.erl"},{line,26}]},
            {rabbit,start,2,[{file,"src/rabbit.erl"},{line,687}]},
            {application_master,start_it_old,4,
                [{file,"application_master.erl"},{line,272}]}]}}

Log files (may contain more information):
   /Applications/Coding/rabbitmq/var/log/rabbitmq/[email protected]
   /Applications/Coding/rabbitmq/var/log/rabbitmq/[email protected]

{"init terminating in do_boot",{could_not_start,rabbit,{undef,[{crypto,module_info,[attributes],[]},{rabbit_misc,module_attributes,1,[{file,"src/rabbit_misc.erl"},{line,798}]},{rabbit_misc,'-all_module_attributes/1-fun-0-',3,[{file,"src/rabbit_misc.erl"},{line,818}]},{lists,foldl,3,[{file,"lists.erl"},{line,1261}]},{rabbit_boot_steps,find_steps,1,[{file,"src/rabbit_boot_steps.erl"},{line,40}]},{rabbit_boot_steps,run_boot_steps,1,[{file,"src/rabbit_boot_steps.erl"},{line,26}]},{rabbit,start,2,[{file,"src/rabbit.erl"},{line,687}]},{application_master,start_it_old,4,[{file,"application_master.erl"},{line,272}]}]}}}

Crash dump was written to: erl_crash.dump
init terminating in do_boot ()

After a while, I found that Erlang had not been installed. I had previously re installed homebrew. I suspected that I had uninstalled it before

Re install Erlang

$ brew install erlang
Updating Homebrew...
==> Installing dependencies for erlang: openssl, jpeg, libpng, libtiff, wxmac
==> Installing erlang dependency: openssl
==> Downloading https://homebrew.bintray.com/bottles/openssl-1.0.2k.el_capitan.bottle.tar.gz
######################################################################## 100.0%
==> Pouring openssl-1.0.2k.el_capitan.bottle.tar.gz
==> Using the sandbox
==> Caveats
A CA file has been bootstrapped using certificates from the SystemRoots
keychain. To add additional certificates (e.g. the certificates added in
the System keychain), place .pem files in
  /usr/local/etc/openssl/certs

and run
  /usr/local/opt/openssl/bin/c_rehash

This formula is keg-only, which means it was not symlinked into /usr/local.

Apple has deprecated use of OpenSSL in favor of its own TLS and crypto libraries

If you need to have this software first in your PATH run:
  echo 'export PATH="/usr/local/opt/openssl/bin:$PATH"' >> ~/.bash_profile

For compilers to find this software you may need to set:
    LDFLAGS:  -L/usr/local/opt/openssl/lib
    CPPFLAGS: -I/usr/local/opt/openssl/include

==> Summary