Makefile: Add requirements-python26

To simplify usage with python2.6 add requirements-python26.txt which
adds python2.6 requirements (on top of requirements.txt). It includes
booth avocado and selftest dependencies and is automatically invoked
when running on system with python 2.6.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

Makefile

@@ -99,6 +99,7 @@ install-requirements-all: install-requirements install-requirements-selftests
 
 install-requirements:
 	grep -v '^#' requirements.txt | xargs -n 1 pip install --upgrade
+	if $$(python -V 2>&1 | grep 2.6 -q); then grep -v '^#' requirements-python26.txt | xargs -n 1 pip install --upgrade; fi
 
 install-requirements-selftests:
 	grep -v '^#' requirements-selftests.txt | xargs -n 1 pip install --upgrade

requirements-python26.txt

+# Additional python 2.6 specific requirements for avocado and unittests (backports)
+argparse>=1.3.0
+logutils>=0.3.3
+importlib>=1.0.3
+unittest2>=1.0.0