Update screenshot_test.py

Author: JE-Chen

test/unit_test/screen/screenshot_test.py

@@ -7,7 +7,7 @@
 assert (image is not None)
 print(image)
 
-subprocess.call("notepad.exe")
+subprocess.Popen("notepad.exe", stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, shell=True)
 
 # screenshot and save
 image = screenshot("test.png")