Fix crash for service_only's bootstrap on create_python_bundle

When building an apk for service_only's bootstrap using the testapp_service the build suddenly crash, because we don't installed any pure python package, so, the directory "python-install/<distribution directory>" doesn't exist. This makes p4a crash when we tried to enter into this directory.

Author: opacam

pythonforandroid/python.py

@@ -358,6 +358,7 @@ def create_python_bundle(self, dirn, arch):
 
         # copy the site-packages into place
         ensure_dir(join(dirn, 'site-packages'))
+        ensure_dir(self.ctx.get_python_install_dir())
         # TODO: Improve the API around walking and copying the files
         with current_directory(self.ctx.get_python_install_dir()):
             filens = list(walk_valid_filens(