diff --git a/src/z3c/rml/attr.py b/src/z3c/rml/attr.py
index abf8d18..5bbc80c 100644
--- a/src/z3c/rml/attr.py
+++ b/src/z3c/rml/attr.py
@@ -92,7 +92,7 @@ def get(self):
         if (interfaces.IDeprecated.providedBy(self) and
             self.deprecatedName in self.context.element.attrib):
             name = self.deprecatedName
-            logger.warn(
+            logger.warning(
                 u'Deprecated attribute "%s": %s %s' % (
                 name, self.deprecatedReason, getFileInfo(self.context)))
         else:
diff --git a/src/z3c/rml/directive.py b/src/z3c/rml/directive.py
index 8e27027..14847df 100644
--- a/src/z3c/rml/directive.py
+++ b/src/z3c/rml/directive.py
@@ -108,7 +108,7 @@ def processSubDirectives(self, select=None, ignore=None):
                 msg = "Directive %r could not be processed and was " \
                       "ignored. %s" %(element.tag, getFileInfo(self, element))
                 # Record any tags/elements that could not be processed.
-                logger.warn(msg)
+                logger.warning(msg)
                 if ABORT_ON_INVALID_DIRECTIVE:
                     raise ValueError(msg)
                 continue
diff --git a/src/z3c/rml/pagetemplate.txt b/src/z3c/rml/pagetemplate.txt
index e99cf02..9c886d4 100644
--- a/src/z3c/rml/pagetemplate.txt
+++ b/src/z3c/rml/pagetemplate.txt
@@ -13,7 +13,8 @@ The first step is to create a page template:
 
   >>> import tempfile
   >>> ptFileName = tempfile.mktemp('.pt')
-  >>> open(ptFileName, 'w').write('''\
+  >>> file_ = open(ptFileName, 'w')
+  >>> file_.write('''\
   ... <?xml version="1.0" encoding="UTF-8" ?>
   ... <!DOCTYPE document SYSTEM "rml.dtd">
   ... <document filename="template.pdf"
@@ -35,6 +36,7 @@ The first step is to create a page template:
   ... </document>
   ... ''')
   463
+  >>> file_.close()
 
 The ``context`` namespace will be created during rendering. I get back to this
 later. In th enext step we instantiate the page template:
diff --git a/src/z3c/rml/reference.py b/src/z3c/rml/reference.py
index 9227c64..01a2617 100644
--- a/src/z3c/rml/reference.py
+++ b/src/z3c/rml/reference.py
@@ -226,6 +226,8 @@ def extractExamples(directory):
                 xml = highlightRML(xml)
                 example['code'] = xml
 
+        rmlFile.close()
+
     return examples
 
 
@@ -239,4 +241,6 @@ def main(outPath=None):
     directives = sorted(directives.values(), key=lambda d: d['name'])
 
     pdf = template(types=getAttributeTypes(), directives=directives)
-    open(outPath or 'rml-reference.pdf', 'wb').write(pdf)
+    file_ = open(outPath or 'rml-reference.pdf', 'wb')
+    file_.write(pdf)
+    file_.close()
diff --git a/src/z3c/rml/rml2pdf.py b/src/z3c/rml/rml2pdf.py
index 5c6e88c..e6dfcfd 100644
--- a/src/z3c/rml/rml2pdf.py
+++ b/src/z3c/rml/rml2pdf.py
@@ -60,6 +60,10 @@ def go(xmlInputName, outputFileName=None, outDir=None, dtdDir=None):
     # Create a Reportlab canvas by processing the document
     doc.process(outputFile)
 
+    if outputFile:
+        outputFile.close()
+    xmlFile.close()
+
 
 def main(args=None):
     if args is None:
diff --git a/src/z3c/rml/tests/test_rml.py b/src/z3c/rml/tests/test_rml.py
index 53c0676..128d3a9 100644
--- a/src/z3c/rml/tests/test_rml.py
+++ b/src/z3c/rml/tests/test_rml.py
@@ -84,13 +84,17 @@ def __init__(self, basePath, testPath):
         unittest.TestCase.__init__(self)
 
     def assertSameImage(self, baseImage, testImage):
-        base = Image.open(baseImage).getdata()
-        test = Image.open(testImage).getdata()
+        base_file = open(baseImage, 'rb')
+        test_file = open(testImage, 'rb')
+        base = Image.open(base_file).getdata()
+        test = Image.open(test_file).getdata()
         for i in range(len(base)):
             if (base[i] - test[i]) != 0:
                 self.fail(
                     'Image is not the same: %s' % os.path.basename(baseImage)
                 )
+        base_file.close()
+        test_file.close()
 
     def runTest(self):
         # Convert the base PDF to image(s)