Split test requirements to try and properly minimize dependencies

requirements-test-db.txt

+pytest-postgresql

requirements-test.txt

 pytest
-pytest-postgresql
 requests-mock
 hypothesis >= 3.11.0
 pre-commit

setup.py

@@ -51,10 +51,14 @@ setup(
     install_requires=parse_requirements(None, 'swh'),
     setup_requires=['vcversioner'],
     extras_require={
-        'testing': parse_requirements('test', 'db', 'http', 'logging'),
+        'testing-core': parse_requirements('test'),
         'logging': parse_requirements('logging'),
         'db': parse_requirements('db'),
+        'testing-db': parse_requirements('test-db'),
         'http': parse_requirements('http'),
+        # kitchen sink, please do not use
+        'testing': parse_requirements('test', 'test-db', 'db', 'http',
+                                      'logging'),
     },
     vcversioner={},
     include_package_data=True,

tox.ini

@@ -3,9 +3,9 @@ envlist=flake8,mypy,py3-{core,db,server}
 
 [testenv]
 deps =
-  -rrequirements-test.txt
-  core: -rrequirements-logging.txt
-  db: .[db]
+  .[testing-core]
+  core: .[logging]
+  db: .[db,testing-db]
   db: pifpaf
   server: .[http]
   cover: pytest-cov
@@ -34,7 +34,7 @@ commands =
 [testenv:mypy]
 skip_install = true
 deps =
-  .[testing]
+  .[logging,db,http,testing-core,testing-db]
   mypy
 commands =
   mypy swh