python 2.6 support for pytest and ansible 2.6

Removed `mock` from the `testenv` `deps`.
Added `mock` to the template pytest_extra_requirements.txt,
commented out.  Projects such as network that need it can uncomment it.

.travis/preinstall

@@ -20,6 +20,11 @@ if lsr_venv_python_matches_system_python; then
   LSR_EXTRA_PACKAGES='python3-selinux'
 fi
 
+# extra packages needed with python 2.6 and ansible 2.6
+if lsr_check_python_version python -lt 2.7 ; then
+  LSR_EXTRA_PACKAGES="$LSR_EXTRA_PACKAGES libffi-dev libssl-dev"
+fi
+
 . ${SCRIPTDIR}/config.sh
 
 # Install extra dependencies.

ansible_pytest_extra_requirements.txt

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: MIT
+
+# ansible and dependencies for all supported platforms
+ansible ; python_version > "2.6"
+ansible<2.7 ; python_version < "2.7"
+idna<2.8 ; python_version < "2.7"
+PyYAML<5.1 ; python_version < "2.7"

pytest_extra_requirements.txt

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: MIT
+
+# Write extra requirements for running pytest here:
+# If you need ansible then uncomment the following line:
+#-ransible_pytest_extra_requirements.txt
+# If you need mock then uncomment the following line:
+mock ; python_version < "3.0"

tox.ini

@@ -13,8 +13,8 @@ basepython = python3
 deps =
     py{26,27,36,37,38}: pytest-cov
     py{27,36,37,38}: pytest>=3.5.1
-    py{26,27}: mock
     py26: pytest
+    py{26,27,36,37,38}: -rpytest_extra_requirements.txt
 
 [base]
 passenv = *