diff --git a/python/mozbuild/mozbuild/configure/util.py b/python/mozbuild/mozbuild/configure/util.py
index 8628c5588977..8120b071ff19 100644
--- a/python/mozbuild/mozbuild/configure/util.py
+++ b/python/mozbuild/mozbuild/configure/util.py
@@ -54,11 +54,30 @@ class Version(LooseVersion):
             itertools.takewhile(lambda x: isinstance(x, int), self.version),
             (0, 0, 0)))[:3]
 
-    def __cmp__(self, other):
+    def _cmp(self, other):
         # LooseVersion checks isinstance(StringType), so work around it.
-        if isinstance(other, six.text_type):
+        if six.PY2 and isinstance(other, six.text_type):
             other = other.encode('ascii')
-        return LooseVersion.__cmp__(self, other)
+        if six.PY2:
+            return LooseVersion.__cmp__(self, other)
+        return LooseVersion._cmp(self, other)
+
+    # These method definitions can be deleted when we remove support for Python
+    # 2.
+    def __eq__(self, other):
+        return self._cmp(other) == 0
+
+    def __lt__(self, other):
+        return self._cmp(other) < 0
+
+    def __le__(self, other):
+        return self._cmp(other) <= 0
+
+    def __gt__(self, other):
+        return self._cmp(other) > 0
+
+    def __ge__(self, other):
+        return self._cmp(other) >= 0
 
 
 class ConfigureOutputHandler(logging.Handler):
diff --git a/python/mozbuild/mozbuild/frontend/context.py b/python/mozbuild/mozbuild/frontend/context.py
index 64acc355944b..3394115eee53 100644
--- a/python/mozbuild/mozbuild/frontend/context.py
+++ b/python/mozbuild/mozbuild/frontend/context.py
@@ -704,29 +704,39 @@ class Path(ContextDerivedValue, six.text_type):
         return Path(self.context, mozpath.join(self, *p))
 
     def __cmp__(self, other):
-        if isinstance(other, Path) and self.srcdir != other.srcdir:
-            return cmp(self.full_path, other.full_path)
-        return cmp(six.text_type(self), other)
+        # We expect this function to never be called to avoid issues in the
+        # switch from Python 2 to 3.
+        raise AssertionError()
 
-    # __cmp__ is not enough because unicode has __eq__, __ne__, etc. defined
-    # and __cmp__ is only used for those when they don't exist.
     def __eq__(self, other):
-        return self.__cmp__(other) == 0
+        if isinstance(other, Path) and self.srcdir != other.srcdir:
+            return self.full_path == other.full_path
+        return six.text_type(self) == other
 
     def __ne__(self, other):
-        return self.__cmp__(other) != 0
+        if isinstance(other, Path) and self.srcdir != other.srcdir:
+            return self.full_path != other.full_path
+        return six.text_type(self) != other
 
     def __lt__(self, other):
-        return self.__cmp__(other) < 0
+        if isinstance(other, Path) and self.srcdir != other.srcdir:
+            return self.full_path < other.full_path
+        return six.text_type(self) < other
 
     def __gt__(self, other):
-        return self.__cmp__(other) > 0
+        if isinstance(other, Path) and self.srcdir != other.srcdir:
+            return self.full_path > other.full_path
+        return six.text_type(self) > other
 
     def __le__(self, other):
-        return self.__cmp__(other) <= 0
+        if isinstance(other, Path) and self.srcdir != other.srcdir:
+            return self.full_path <= other.full_path
+        return six.text_type(self) <= other
 
     def __ge__(self, other):
-        return self.__cmp__(other) >= 0
+        if isinstance(other, Path) and self.srcdir != other.srcdir:
+            return self.full_path >= other.full_path
+        return six.text_type(self) >= other
 
     def __repr__(self):
         return '<%s (%s)%s>' % (self.__class__.__name__, self.srcdir, self)
diff --git a/python/mozbuild/mozbuild/test/frontend/test_namespaces.py b/python/mozbuild/mozbuild/test/frontend/test_namespaces.py
index 630c94b43ad5..b434dbf6ba11 100644
--- a/python/mozbuild/mozbuild/test/frontend/test_namespaces.py
+++ b/python/mozbuild/mozbuild/test/frontend/test_namespaces.py
@@ -4,6 +4,7 @@
 
 from __future__ import absolute_import, print_function, unicode_literals
 
+import six
 import unittest
 
 from mozunit import main
@@ -29,7 +30,7 @@ class Fuga(object):
 
 class Piyo(ContextDerivedValue):
     def __init__(self, context, value):
-        if not isinstance(value, unicode):
+        if not isinstance(value, six.text_type):
             raise ValueError
         self.context = context
         self.value = value
@@ -40,17 +41,29 @@ class Piyo(ContextDerivedValue):
     def __str__(self):
         return self.value
 
-    def __cmp__(self, other):
-        return cmp(self.value, str(other))
+    def __eq__(self, other):
+        return self.value == six.text_type(other)
+
+    def __lt__(self, other):
+        return self.value < six.text_type(other)
+
+    def __le__(self, other):
+        return self.value <= six.text_type(other)
+
+    def __gt__(self, other):
+        return self.value > six.text_type(other)
+
+    def __ge__(self, other):
+        return self.value >= six.text_type(other)
 
     def __hash__(self):
         return hash(self.value)
 
 
 VARIABLES = {
-    'HOGE': (unicode, unicode, None),
-    'FUGA': (Fuga, unicode, None),
-    'PIYO': (Piyo, unicode, None),
+    'HOGE': (six.text_type, six.text_type, None),
+    'FUGA': (Fuga, six.text_type, None),
+    'PIYO': (Piyo, six.text_type, None),
     'HOGERA': (ContextDerivedTypedList(Piyo, StrictOrderingOnAppendList),
                list, None),
     'HOGEHOGE': (ContextDerivedTypedListWithItems(
@@ -105,7 +118,7 @@ class TestContext(unittest.TestCase):
         self.assertEqual(e[1], 'set_type')
         self.assertEqual(e[2], 'HOGE')
         self.assertEqual(e[3], True)
-        self.assertEqual(e[4], unicode)
+        self.assertEqual(e[4], six.text_type)
 
     def test_key_checking(self):
         # Checking for existence of a key should not populate the key if it
@@ -128,7 +141,7 @@ class TestContext(unittest.TestCase):
         self.assertEqual(e[1], 'set_type')
         self.assertEqual(e[2], 'FUGA')
         self.assertEqual(e[3], False)
-        self.assertEqual(e[4], unicode)
+        self.assertEqual(e[4], six.text_type)
 
         ns['FUGA'] = 'fuga'
         self.assertIsInstance(ns['FUGA'], Fuga)
@@ -151,7 +164,7 @@ class TestContext(unittest.TestCase):
         self.assertEqual(e[1], 'set_type')
         self.assertEqual(e[2], 'PIYO')
         self.assertEqual(e[3], False)
-        self.assertEqual(e[4], unicode)
+        self.assertEqual(e[4], six.text_type)
 
         ns['PIYO'] = 'piyo'
         self.assertIsInstance(ns['PIYO'], Piyo)
diff --git a/python/mozrelease/mozrelease/versions.py b/python/mozrelease/mozrelease/versions.py
index 8d40c05717fb..1bcf0f3ddb68 100644
--- a/python/mozrelease/mozrelease/versions.py
+++ b/python/mozrelease/mozrelease/versions.py
@@ -6,10 +6,25 @@ from __future__ import absolute_import
 
 from distutils.version import StrictVersion, LooseVersion
 import re
+from six import PY2
+
+
+def _cmp(cls, first, other):
+    # Because the __cmp__ metamethod was removed in the switch to Python 3, the
+    # interface of the distutils.version.*Version classes changed in a
+    # backwards-incompatible way. Call this instead of first.__cmp__(other) or
+    # first._cmp(other) to handle both possibilities.
+    if PY2:
+        return cls.__cmp__(first, other)
+    return cls._cmp(first, other)
 
 
 class MozillaVersionCompareMixin():
     def __cmp__(self, other):
+        # We expect this function to never be called.
+        raise AssertionError()
+
+    def _cmp(self, other):
         has_esr = set()
         if isinstance(other, LooseModernMozillaVersion) and str(other).endswith('esr'):
             # If other version ends with esr, coerce through MozillaVersion ending up with
@@ -25,15 +40,15 @@ class MozillaVersionCompareMixin():
                 isinstance(self, LooseModernMozillaVersion):
             # If we're still LooseVersion for self or other, run LooseVersion compare
             # Being sure to pass through Loose Version type first
-            val = LooseVersion.__cmp__(
-                    LooseModernMozillaVersion(str(self)),
-                    LooseModernMozillaVersion(str(other)))
+            val = _cmp(LooseVersion,
+                       LooseModernMozillaVersion(str(self)),
+                       LooseModernMozillaVersion(str(other)))
         else:
             # No versions are loose, therefore we can use StrictVersion
-            val = StrictVersion.__cmp__(self, other)
+            val = _cmp(StrictVersion, self, other)
         if has_esr.isdisjoint(set(['other', 'self'])) or \
                 has_esr.issuperset(set(['other', 'self'])):
-            #  If both had esr string or neither, then cmp() was accurate
+            #  If both had esr string or neither, then _cmp() was accurate
             return val
         elif val != 0:
             # cmp is accurate here even if esr is present in only 1 compare, since
@@ -43,6 +58,22 @@ class MozillaVersionCompareMixin():
             return -1  # esr is not greater than non esr
         return 1  # non esr is greater than esr
 
+    # These method definitions can be deleted when we drop support for Python 2.
+    def __eq__(self, other):
+        return self._cmp(other) == 0
+
+    def __lt__(self, other):
+        return self._cmp(other) < 0
+
+    def __le__(self, other):
+        return self._cmp(other) <= 0
+
+    def __gt__(self, other):
+        return self._cmp(other) > 0
+
+    def __ge__(self, other):
+        return self._cmp(other) >= 0
+
 
 class ModernMozillaVersion(MozillaVersionCompareMixin, StrictVersion):
     """A version class that is slightly less restrictive than StrictVersion.
diff --git a/python/mozrelease/test/python.ini b/python/mozrelease/test/python.ini
index 8d3588d7b23b..7cbba389afd6 100644
--- a/python/mozrelease/test/python.ini
+++ b/python/mozrelease/test/python.ini
@@ -2,7 +2,6 @@
 subsuite=mozrelease
 
 [test_versions.py]
-skip-if = python == 3
 [test_update_verify.py]
 skip-if = python == 3
 [test_balrog.py]