Unclear error message when trying to authenticate with wrong password: E409 Conflict

My reason:

I’m getting the following error message from NPM 5 while trying to authenticate with a wrong password:

[mac ~]# npm login --registry http://localhost:4873
Username: username
Password: 
Email: (this IS public) user@email.com
npm ERR! code E409
npm ERR! Conflict

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/user/.npm/_logs/2017-12-20T12_39_01_443Z-debug.log
[mac ~]#

Steps to reproduce:

Try to npm login with an incorrect password.

App Version:

Verdaccio 2.7.0 NodeJS v8.9.3 NPM 5.5.1

Config file:

storage: /storage
uplinks:
  npmjs:
    url: https://registry.npmjs.org/
    auth:
      type: bearer
      token: xxx 
packages:
  '@*/*':
    access: $authenticated
    publish: $authenticated
    proxy: npmjs
  '**':
    access: $all
    publish: $authenticated
    proxy: npmjs
logs:
  - {type: stdout, format: pretty, level: info}
auth:
  ldap:
    type: ldap
    groupNameAttribute: cn
    client_options:
      url: ldaps://local.ad
      adminDn: admin@ad.net
      adminPassword: xxxx
      searchBase: OU=users,DC=ad,DC=net
      searchFilter: (sAMAccountName={{username}})
      searchAttributes:
        - memberOf

Additional information:

It seems that NPM 5 expects 401 status code and the www-authenticate header to be set to display a proper error message:

[mac ~]# npm login --registry https://registry.npmjs.org
Username: username
Password: 
Email: (this IS public) user@email.com
npm ERR! code E401
npm ERR! Incorrect or missing password.
npm ERR! If you were trying to login, change your password, create an
<...>

but Verdaccio overrides response status code to be 409.

Additional verbose log:

Verdaccio log:

<...>
 http <-- 409, user: undefined(127.0.0.1), req: 'PUT /-/user/org.couchdb.user:username', error: bad username/password, access denied
 info <-- 127.0.0.1 requested 'GET /-/user/org.couchdb.user:username?write=true'
 http <-- 200, user: undefined(127.0.0.1), req: 'GET /-/user/org.couchdb.user:username?write=true', bytes: 0/53
 info <-- 127.0.0.1 requested 'PUT /-/user/org.couchdb.user:username/-rev/undefined'
 warn --- LDAP error no such user: "username"
 warn --- LDAP error no such user: "username"
 http <-- 409, user: undefined(127.0.0.1), req: 'PUT /-/user/org.couchdb.user:username/-rev/undefined', error: bad username/password, access denied
 info <-- 127.0.0.1 requested 'PUT /-/user/org.couchdb.user:username'
 warn --- LDAP error no such user: "username"
 http <-- 409, user: undefined(127.0.0.1), req: 'PUT /-/user/org.couchdb.user:username', error: bad username/password, access denied
<...>