Fixes issue 1571:

Adding missing close for open.
If the "close()" call is missing after a "open(filename)" call, the filename isn't guaranteed to be closed before the interpreter exits.
This is generally a bad practice as explained here: https://stackoverflow.com/questions/7395542/is-explicitly-closing-files-important

Also replaced "fid=open(filename) fid.close()" statements for files with the safer
"with open(filename) as fid:" blocks. See https://www.python.org/dev/peps/pep-0343/

demo/agw/RulerCtrl.py

@@ -157,12 +157,12 @@ class RulerCtrlDemo(wx.Frame):
 
         self.stc = PythonSTC(self.panel, -1)
         try:
-            fid = open("RulerCtrl.py", "rt")
+            with open("RulerCtrl.py", "rt") as fid:
+                text = fid.read()
         except:
-            fid = open("agw/RulerCtrl.py", "rt")
+            with open("agw/RulerCtrl.py", "rt") as fid:
+                text = fid.read()
 
-        text = fid.read()
-        fid.close()
         self.stc.SetValue(text)
 
         self.ruler1 = RC.RulerCtrl(self.panel, -1, orient=wx.HORIZONTAL, style=wx.SUNKEN_BORDER)

demo/agw/ShortcutEditor.py

@@ -387,8 +387,8 @@ def runTest(frame, nb, log):
 
 #----------------------------------------------------------------------
 
-
-overview = open(HTML_HELP, 'rt').read()
+with open(HTML_HELP, 'rt') as fid:
+    overview = fid.read()
 
 
 if __name__ == '__main__':