diff --git a/dulwich/contrib/release_robot.py b/dulwich/contrib/release_robot.py
index e32daa9d..ea951db0 100644
--- a/dulwich/contrib/release_robot.py
+++ b/dulwich/contrib/release_robot.py
@@ -1,110 +1,110 @@
 """Determine last version string from tags.
 
 Alternate to `Versioneer <https://pypi.python.org/pypi/versioneer/>`_ using
 `Dulwich <https://pypi.python.org/pypi/dulwich>`_ to sort tags by time from
 newest to oldest.
 
 Import this module into the package ``__init__.py`` and then set ``__version__``
 as follows::
 
     from dulwich.contrib.release_robot import get_current_version
 
     __version__ = get_current_version()
     # other dunder classes like __author__, etc.
 
 This example assumes the tags have a leading "v" like "v0.3", and that the
 ``.git`` folder is in the project folder that containts the package folder.
 """
 
 from dulwich.repo import Repo
 import time
 import datetime
 import os
 import re
 import sys
 
 # CONSTANTS
 DIRNAME = os.path.abspath(os.path.dirname(__file__))
 PROJDIR = os.path.dirname(DIRNAME)
 PATTERN = '[ a-zA-Z_\-]*([\d\.]+[\-\w\.]*)'
 
 
 def get_recent_tags(projdir=PROJDIR):
     """Get list of tags in order from newest to oldest and their datetimes.
 
     :param projdir: path to ``.git``
     :returns: list of (tag, [datetime, commit, author]) sorted from new to old
     """
     project = Repo(projdir)  # dulwich repository object
     refs = project.get_refs()  # dictionary of refs and their SHA-1 values
     tags = {}  # empty dictionary to hold tags, commits and datetimes
     # iterate over refs in repository
-    for key, value in refs.iteritems():
+    for key, value in refs.items():
         obj = project.get_object(value)  # dulwich object from SHA-1
         # check if object is tag
         if obj.type_name != 'tag':
             # skip ref if not a tag
             continue
         # strip the leading text from "refs/tag/<tag name>" to get "tag name"
         _, tag = key.rsplit('/', 1)
         # check if tag object is commit, altho it should always be true
         if obj.object[0].type_name == 'commit':
             commit = project.get_object(obj.object[1])  # commit object
             # get tag commit datetime, but dulwich returns seconds since
             # beginning of epoch, so use Python time module to convert it to
             # timetuple then convert to datetime
             tags[tag] = [
                 datetime.datetime(*time.gmtime(commit.commit_time)[:6]),
                 commit.id,
                 commit.author
             ]
 
     # return list of tags sorted by their datetimes from newest to oldest
-    return sorted(tags.iteritems(), key=lambda tag: tag[1][0], reverse=True)
+    return sorted(tags.items(), key=lambda tag: tag[1][0], reverse=True)
 
 
 def get_current_version(pattern=PATTERN, projdir=PROJDIR, logger=None):
     """Return the most recent tag, using an options regular expression pattern.
 
     The default pattern will strip any characters preceding the first semantic
     version. *EG*: "Release-0.2.1-rc.1" will be come "0.2.1-rc.1". If no match
     is found, then the most recent tag is return without modification.
 
     :param pattern: regular expression pattern with group that matches version
     :param projdir: path to ``.git``
     :param logger: a Python logging instance to capture exception
     :returns: tag matching first group in regular expression pattern
     """
     tags = get_recent_tags(projdir)
     try:
         tag = tags[0][0]
     except IndexError:
         return
     m = re.match(pattern, tag)
     try:
         current_version = m.group(1)
     except (IndexError, AttributeError) as err:
         if logger:
             logger.exception(err)
         return tag
     return current_version
 
 
 def test_tag_pattern():
     test_cases = {
         '0.3': '0.3', 'v0.3': '0.3', 'release0.3': '0.3', 'Release-0.3': '0.3',
         'v0.3rc1': '0.3rc1', 'v0.3-rc1': '0.3-rc1', 'v0.3-rc.1': '0.3-rc.1',
         'version 0.3': '0.3', 'version_0.3_rc_1': '0.3_rc_1', 'v1': '1',
         '0.3rc1': '0.3rc1'
     }
     for tc, version in test_cases.iteritems():
         m = re.match(PATTERN, tc)
         assert m.group(1) == version
 
 
 if __name__ == '__main__':
     if len(sys.argv) > 1:
         projdir = sys.argv[1]
     else:
         projdir = PROJDIR
-    print get_current_version(projdir=projdir)
+    print(get_current_version(projdir=projdir))