python-cheetah: fix python host dependency

python-cheetah can't be used with python3. host-python-cheetah has the same
limitation.

Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/python-cheetah/python-cheetah.mk

@@ -10,6 +10,8 @@ PYTHON_CHEETAH_SITE = http://pypi.python.org/packages/source/C/Cheetah
 PYTHON_CHEETAH_LICENSE = MIT
 PYTHON_CHEETAH_SETUP_TYPE = setuptools
 
+HOST_PYTHON_CHEETAH_NEEDS_HOST_PYTHON = python2
+
 # The dependency on host-python-markdown is needed to prevent
 # setuptools from downloading markdown if it is not installed yet.
 HOST_PYTHON_CHEETAH_DEPENDENCIES = host-python-markdown