Fixed an issue where __init__.check_dt_compatible_value opened a file…

[fpdotmonkey]

… but did not close it and thus caused a memory leak and a ResourceWarning.

I also wrote this test program to verify that my change worked. If it would be helpful, I can add it to the repo in an additional commit.

#
# Run this test with `python3 -m unittest` in 
# `Adafruit_Python_PlatformDetect/adafruit_platformdetect`
#
import unittest
import warnings

from __init__ import Detector


class TestDetector(unittest.TestCase):

    def test_check_dt_compatible_value_closes_file(self):
        detector = Detector()
        with warnings.catch_warnings(record=True) as warning:
            warnings.simplefilter("default", category=ResourceWarning)
            detector.check_dt_compatible_value("test")
            self.assertEquals(len(warning), 0,
                              "The file `/proc/device-tree/compatible` "
                              "is not\nbeing closed and Detector is "
                              "leaking memory.")

[makermelissa]

Thanks for finding and fixing this.