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/

wx/lib/pubsub/core/topicdefnprovider.py

@@ -277,9 +277,8 @@ class TopicDefnDeserialString(ITopicDefnDeserializer):
             import os, tempfile
             creationDir = os.getcwd()
             fileID, path = tempfile.mkstemp('.py', moduleNamePre, dir=creationDir)
-            stringFile = os.fdopen(fileID, 'w')
-            stringFile.write( dedent(source) )
-            stringFile.close()
+            with os.fdopen(fileID, 'w') as stringFile:
+                stringFile.write( dedent(source) )
             return path, [creationDir]
 
         self.__filename, searchPath = createTmpModule()
@@ -443,11 +442,11 @@ def exportTopicTreeSpec(moduleName = None, rootTopic=None, bak='bak', moduleDoc=
         filename = '%s.py' % moduleName
         if bak:
             _backupIfExists(filename, bak)
-        moduleFile = open(filename, 'w')
-        try:
-            TopicTreeSpecPrinter(rootTopic, fileObj=moduleFile, treeDoc=moduleDoc)
-        finally:
-            moduleFile.close()
+        with open(filename, 'w') as moduleFile:
+            try:
+                TopicTreeSpecPrinter(rootTopic, fileObj=moduleFile, treeDoc=moduleDoc)
+            finally:
+                pass
 
 ##############################################################
 

wx/lib/pubsub/utils/xmltopicdefnprovider.py

@@ -1,9 +1,9 @@
 """
-Contributed by Joshua R English, adapted by Oliver Schoenborn to be 
-consistent with pubsub API. 
+Contributed by Joshua R English, adapted by Oliver Schoenborn to be
+consistent with pubsub API.
 
-An extension for pubsub (http://pubsub.sourceforge.net) so topic tree 
-specification can be encoded in XML format rather than pubsub's default 
+An extension for pubsub (http://pubsub.sourceforge.net) so topic tree
+specification can be encoded in XML format rather than pubsub's default
 Python nested class format.
 
 To use:
@@ -32,7 +32,7 @@ These topic definitions are loaded through an XmlTopicDefnProvider:
 
     pub.addTopicDefnProvider( XmlTopicDefnProvider(xml) )
 
-The XmlTopicDefnProvider also accepts a filename instead of XML string: 
+The XmlTopicDefnProvider also accepts a filename instead of XML string:
 
     provider = XmlTopicDefnProvider("path/to/XMLfile.xml", TOPIC_TREE_FROM_FILE)
     pub.addTopicDefnProvider( provider )
@@ -72,7 +72,7 @@ __all__ = [
     'TOPIC_TREE_FROM_FILE'
     ]
 
-    
+
 def _get_elem(elem):
     """Assume an ETree.Element object or a string representation.
     Return the ETree.Element object"""
@@ -84,7 +84,7 @@ def _get_elem(elem):
             raise ValueError("Cannot convert to element")
     return elem
 
-    
+
 TOPIC_TREE_FROM_FILE = 'file'
 
 
@@ -93,12 +93,13 @@ class XmlTopicDefnProvider(ITopicDefnProvider):
     class XmlParserError(RuntimeError): pass
 
     class UnrecognizedSourceFormatError(ValueError): pass
-    
+
     def __init__(self, xml, format=TOPIC_TREE_FROM_STRING):
         self._topics = {}
         self._treeDoc = ''
         if format == TOPIC_TREE_FROM_FILE:
-            self._parse_tree(_get_elem(open(xml,mode="r").read()))
+            with open(xml, mode="r") as fid:
+                self._parse_tree(_get_elem(fid.read()))
         elif format == TOPIC_TREE_FROM_STRING:
             self._parse_tree(_get_elem(xml))
         else:
@@ -164,7 +165,7 @@ class XmlTopicDefnProvider(ITopicDefnProvider):
     def getTreeDoc(self):
         return self._treeDoc
 
-    
+
 class XmlVisitor(ITopicTreeVisitor):
     def __init__(self, elem):
         self.tree = elem
@@ -188,7 +189,7 @@ class XmlVisitor(ITopicTreeVisitor):
         desc_elem = ET.SubElement(this_elem, 'description')
         topicDesc = topicObj.getDescription()
         if topicDesc:
-            desc_elem.text = ' '.join(topicDesc.split()) 
+            desc_elem.text = ' '.join(topicDesc.split())
         else:
             desc_elem.text = "UNDOCUMENTED"
         argDescriptions = topicObj.getArgDescriptions()
@@ -228,7 +229,7 @@ class XmlVisitor(ITopicTreeVisitor):
     def _endChildren(self):
         self.roots.pop()
 
-        
+
 ## http://infix.se/2007/02/06/gentlemen-indent-your-xml
 def indent(elem, level=0):
     i = "\n" + level*"    "