Split dev_requirements.txt up according to test mode.

dev_requirements.txt

@@ -1,19 +1,11 @@
--r docs/docs-requirements.txt
+# This file is no longer used by CI jobs, it's mostly for interactive use.
+# Instead CI jobs grab the relevant sub-requirement.
+
+# mitogen_tests
+-r tests/requirements.txt
+
+# ansible_tests
 -r tests/ansible/requirements.txt
-psutil==5.4.8
-coverage==4.5.1
-Django==1.6.11  # Last version supporting 2.6.
-mock==2.0.0
-pytz==2018.5
-cffi==1.11.2  # Random pin to try and fix pyparser==2.18 not having effect
-pycparser==2.18  # Last version supporting 2.6.
-faulthandler==3.1; python_version < '3.3'  # used by testlib
-pytest-catchlog==1.2.2
-pytest==3.1.2
-PyYAML==3.11; python_version < '2.7'
-PyYAML==3.12; python_version >= '2.7'
-timeoutcontext==1.2.0
-unittest2==1.1.0
-# Fix InsecurePlatformWarning while creating py26 tox environment
-# https://urllib3.readthedocs.io/en/latest/advanced-usage.html#ssl-warnings
-urllib3[secure]; python_version < '2.7.9'
+
+# readthedocs
+-r docs/requirements.txt

tests/ansible/requirements.txt

@@ -2,3 +2,5 @@ ansible; python_version >= '2.7'
 ansible<2.7; python_version < '2.7'
 paramiko==2.3.2  # Last 2.6-compat version.
 google-api-python-client==1.6.5
+PyYAML==3.11; python_version < '2.7'
+PyYAML==3.12; python_version >= '2.7'

tests/requirements.txt

@@ -0,0 +1,15 @@
+psutil==5.4.8
+coverage==4.5.1
+Django==1.6.11  # Last version supporting 2.6.
+mock==2.0.0
+pytz==2018.5
+cffi==1.11.2  # Random pin to try and fix pyparser==2.18 not having effect
+pycparser==2.18  # Last version supporting 2.6.
+faulthandler==3.1; python_version < '3.3'  # used by testlib
+pytest-catchlog==1.2.2
+pytest==3.1.2
+timeoutcontext==1.2.0
+unittest2==1.1.0
+# Fix InsecurePlatformWarning while creating py26 tox environment
+# https://urllib3.readthedocs.io/en/latest/advanced-usage.html#ssl-warnings
+urllib3[secure]; python_version < '2.7.9'