Hi Striker,
the output of error_log when trying to login is:
[Wed May 22 22:43:50.791861 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: Starting new HTTP connection (1): ipa3.roth.net:80
[Wed May 22 22:43:50.807169 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG:
http://ipa3.roth.net:80 "GET /ipa/session/cookie
HTTP/1.1" 301 250
[Wed May 22 22:43:50.835158 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: Starting new HTTPS connection (1): ipa3.roth.net:443
[Wed May 22 22:43:50.959893 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.178.:43548] ipa: DEBUG:
https://ipa3.roth.net:443 "GET /ipa/session/cookie
HTTP/1.1" 200 0
[Wed May 22 22:43:51.040332 2019] [wsgi:error] [pid 21730:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: WSGI wsgi_dispatch.__call__:
[Wed May 22 22:43:51.042095 2019] [wsgi:error] [pid 21730:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: WSGI jsonserver_session.__call__:
[Wed May 22 22:43:51.043798 2019] [wsgi:error] [pid 21730:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: no ccache, need login
[Wed May 22 22:43:51.046018 2019] [wsgi:error] [pid 21730:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: 401 Unauthorized need login
[Wed May 22 22:43:51.086133 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: WSGI wsgi_dispatch.__call__:
[Wed May 22 22:43:51.088151 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: WSGI KerberosLogin.__call__:
[Wed May 22 22:43:51.089993 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: no ccache, need login
[Wed May 22 22:43:51.092056 2019] [wsgi:error] [pid 21731:tid 2937889584] [remote
192.168.1.22:43548] ipa: DEBUG: 401 Unauthorized need login