checking epmd is started without a crash

[shamis]

executing rebar3 shell when epmd is not running causes a crash log

=SUPERVISOR REPORT==== 5-May-2020::10:44:23.655292 ===
    supervisor: {local,net_sup}
    errorContext: start_error
    reason: {'EXIT',nodistribution}
    offender: [{pid,undefined},
               {id,net_kernel},
               {mfargs,{net_kernel,start_link,
                                   [['[email protected]',longnames],false]}},
               {restart_type,permanent},
               {shutdown,2000},
               {child_type,worker}]
=CRASH REPORT==== 5-May-2020::10:44:23.654275 ===
  crasher:
    initial call: net_kernel:init/1
    pid: <0.550.0>
    registered_name: []
    exception exit: {error,badarg}
      in function  gen_server:init_it/6 (gen_server.erl, line 358)
    ancestors: [net_sup,kernel_sup,<0.46.0>]
    message_queue_len: 0
    messages: []
    links: [#Port<0.49>,<0.547.0>]
    dictionary: [{longnames,true}]
    trap_exit: true
    status: running
    heap_size: 376
    stack_size: 27
    reductions: 11369
  neighbours:

This PR checks if epmd is running using erl_epmd:names/0

[ferd]

erl_epmd:names() is an undocumented function (and erl_epmd:names/1 was added in OTP-21 as per doc and can't be relied on). Did you try with net_adm:names/0 which should potentially be safer to use?

[shamis]

have changed to net_adm:names/0. It is working the same way as well