configure: Require Python 2.7 or newer

All of the supported build platforms documented in qemu-doc.texi
should already support Python 2.7.

Removing support for Python 2.6 will allow us to remove some
compatibility modules we carry in the QEMU tree:

* scripts/argparse.py
* scripts/ordereddict.py

Python 2.6 is also not receiving bug fixes upstream and is not
supported by pylint, which makes it harder to keep the code
compatible with both Python 2 and Python 3.
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20180608143026.20167-1-ehabkost@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NCleber Rosa <crosa@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

configure

@@ -1651,8 +1651,8 @@ fi
 
 # Note that if the Python conditional here evaluates True we will exit
 # with status 1 which is a shell 'false' value.
-if ! $python -c 'import sys; sys.exit(sys.version_info < (2,6))'; then
-  error_exit "Cannot use '$python', Python 2 >= 2.6 or Python 3 is required." \
+if ! $python -c 'import sys; sys.exit(sys.version_info < (2,7))'; then
+  error_exit "Cannot use '$python', Python 2 >= 2.7 or Python 3 is required." \
       "Use --python=/path/to/python to specify a supported Python."
 fi