Let el7 fall back to bundled python-six

RHEL 7 currently ships python-six 1.3.0, which is old enough to lack
some of the features boto/compat.py relies upon.  For now, we let boto
fall back to the bundled copy on rHEL 7 until we have a better solution.

Update python-six to at least version 1.7.3:
https://bugzilla.redhat.com/show_bug.cgi?id=1210896

python-boto.spec

@@ -107,7 +107,12 @@ cloud systems like Eucalyptus, OpenStack and Open Nebula.
 cp -p %{SOURCE1} .
 
 rm -r boto.egg-info
+
+%if ! 0%{?el7}
+# python-six-1.3.0-4.el7 is too old, causes ImportErrors
+# https://bugzilla.redhat.com/show_bug.cgi?id=1210896
 rm -r boto/vendored
+%endif
 
 
 %build