Bad response from token request after team creation auth

Hi Guys,

I can't create a team in a gitlab-mattermost environnement. After authorisation from gitlab SSO i got redirected to the /signup/gitlab/complete and results in a 500 error : Bad response from token request.

i don't use https / certificates, just plain http. I enabled error logging but i don't have the error details shown. I'am using apache on plesk, and gitlab works perfectly

/var/log/gitlab/mattermost/mattermost.log:

[2016/02/14 20:18:42 CET] [DEBG] /signup/gitlab/complete
[2016/02/14 20:18:42 CET] [EROR] /signup/gitlab/complete:AuthorizeOAuthUser code=500 rid=45puht4ewirytdxzw4kcebw5xa uid= ip=XX.XX.XX.XX Bad response from token request [details: ]

gitlab.rb

mattermost['log_enable_file'] = true
mattermost['log_file_level'] = 'DEBUG'
mattermost_external_url 'http://mattermost.mydomain.com'
mattermost_nginx['enable'] = false
mattermost_nginx['redirect_http_to_https'] = false
mattermost['service_use_ssl'] = false

config.json

"LogSettings": {
    "ConsoleEnable": true,
    "ConsoleLevel": "INFO",
    "EnableFile": true,
    "FileLevel": "DEBUG",
    "FileFormat": "",
    "FileLocation": "/var/log/gitlab/mattermost/mattermost.log"
},
"GitLabSettings": {
    "Enable": true,
    "Secret": "mysecret",
    "Id": "myid",
    "Scope": "",
    "AuthEndpoint": "http://gitlab.mydomain.com/oauth/authorize",
    "TokenEndpoint": "http://gitlab.mydomain.com/oauth/token",
    "UserApiEndpoint": "http://gitlab.mydomain.com/api/v3/user"
}

production.log

Started GET
"/oauth/authorize?response_type=code&client_id=e94bcbe68270faa5d259794498c2809132e79e36936f9222474239a7ff724b1e&redirect_uri=http%3A%2F%2Fmattermost.mydomain.com%2Fsignup%2Fgitlab%2Fcomplete&state=eyJhY3Rpb24iOiJzaWdudXAiLCJoYXNoIjoiJDJhJDEwJHg2QmtrRnU5MHkuNlA4ZE02RFUzMy5ONUQvb3FxWjRqT1Q5RnIwOExqdUIuby8xeTlUTW42IiwidGVhbSI6ImFsaWNld29yazAxMjM0NTY3ODkxMDExIn0%3D"
for 78.249.179.124 at 2016-02-14 15:52:10 +0100

Processing by Oauth::AuthorizationsController#new as HTML

Parameters: {"response_type"=>"code",
"client_id"=>"e94bcbe68270faa5d259794498c2809132e79e36936f9222474239a7ff724b1e",

"redirect_uri"=>"http://mattermost.mydomain.com/signup/gitlab/complete",

"state"=>"eyJhY3Rpb24iOiJzaWdudXAiLCJoYXNoIjoiJDJhJDEwJHg2QmtrRnU5MHkuNlA4ZE02RFUzMy5ONUQvb3FxWjRqT1Q5RnIwOExqdUIuby8xeTlUTW42IiwidGVhbSI6ImFsaWNld29yazAxMjM0NTY3ODkxMDExIn0="}

Completed 200 OK in 71ms (Views: 48.9ms | ActiveRecord: 8.1ms)

Started POST "/oauth/authorize" for 78.249.179.124 at 2016-02-14 15:52:13 +0100

Processing by Oauth::AuthorizationsController#create as HTML

Parameters: {"utf8"=>"✓", "authenticity_token"=>"[FILTERED]",

"client_id"=>"e94bcbe68270faa5d259794498c2809132e79e36936f9222474239a7ff724b1e",

"redirect_uri"=>"http://mattermost.mydomain.com/signup/gitlab/complete",

"state"=>"eyJhY3Rpb24iOiJzaWdudXAiLCJoYXNoIjoiJDJhJDEwJHg2QmtrRnU5MHkuNlA4ZE02RFUzMy5ONUQvb3FxWjRqT1Q5RnIwOExqdUIuby8xeTlUTW42IiwidGVhbSI6ImFsaWNld29yazAxMjM0NTY3ODkxMDExIn0=",
"response_type"=>"code", "scope"=>"api"}

Redirected to
http://mattermost.mydomain.com/signup/gitlab/complete?code=54f138af81298e09d994427365dec4b4e64e49661050f2a35b3d85d04f60d3f6&state=eyJhY3Rpb24iOiJzaWdudXAiLCJoYXNoIjoiJDJhJDEwJHg2QmtrRnU5MHkuNlA4ZE02RFUzMy5ONUQvb3FxWjRqT1Q5RnIwOExqdUIuby8xeTlUTW42IiwidGVhbSI6ImFsaWNld29yazAxMjM0NTY3ODkxMDExIn0%3D

Completed 302 Found in 73ms (ActiveRecord: 56.1ms)

can someone help ?