tests: cleanup test code

- remove unused imports in test cases
- fix code smells and code style in conftest.py

test/test_ports/test_VIRTUAL_PORT-single-different-from-single-port.py

@@ -1,4 +1,3 @@
-import pytest
 import re
 
 

test/test_ports/test_VIRTUAL_PORT.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_answer_is_served_from_chosen_port(docker_compose, nginxproxy):
     r = nginxproxy.get("http://web.nginx-proxy.tld/port")
     assert r.status_code == 200

test/test_ports/test_default-80.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_answer_is_served_from_port_80_by_default(docker_compose, nginxproxy):
     r = nginxproxy.get("http://web.nginx-proxy.tld/port")
     assert r.status_code == 200

test/test_ports/test_single-port-not-80.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_answer_is_served_from_exposed_port_even_if_not_80(docker_compose, nginxproxy):
     r = nginxproxy.get("http://web.nginx-proxy.tld/port")
     assert r.status_code == 200