Fix flake8 check for python3.5

Author: rickwu666666

contrib/checkbox-ce-oem/checkbox-provider-ce-oem/bin/button_test.py

@@ -33,7 +33,7 @@ def __init__(self, irq_name: str):
         self.irq_name = irq_name
         # It maps each IRQ number to its list of target CPUs.
         # Example: {35: [0, 1], 36: [2, 3]}
-        self.irq_numbers: Dict[int, List[int]] = {}
+        self.irq_numbers = {}  # type: Dict[int, List[int]]
         self.num_cpus = os.cpu_count()
 
     def _get_irq_numbers(self) -> bool: