Update recipe.py (#2544)

refactoring code with For Else which is more pythonic, concise and efficient

Author: idiomaticrefactoring

pythonforandroid/recipe.py

@@ -728,7 +728,7 @@ def get_recipe(cls, name, ctx):
             if recipe_file is not None:
                 break
 
-        if not recipe_file:
+        else:
             raise ValueError('Recipe does not exist: {}'.format(name))
 
         mod = import_recipe('pythonforandroid.recipes.{}'.format(name), recipe_file)