No __cmp__ or cmp in Python 3 (#429)

* No __cmp__ or cmp in Python 3

* Add rich comparisons

* Simplify using total_ordering decorator

tests/test_tablib_dbfpy_packages_fields.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python
+"""Tests for tablib.packages.dbfpy."""
+
+import unittest
+
+from tablib.packages.dbfpy import fields
+
+
+class DbfFieldDefTestCompareCase(unittest.TestCase):
+    """dbfpy.fields.DbfFieldDef comparison test cases, via child classes."""
+
+    def setUp(self) -> None:
+        self.length = 10
+        self.a = fields.DbfCharacterFieldDef("abc", self.length)
+        self.z = fields.DbfCharacterFieldDef("xyz", self.length)
+        self.a2 = fields.DbfCharacterFieldDef("abc", self.length)
+
+    def test_compare__eq__(self):
+        # Act / Assert
+        self.assertEqual(self.a, self.a2)
+
+    def test_compare__ne__(self):
+        # Act / Assert
+        self.assertNotEqual(self.a, self.z)
+
+    def test_compare__lt__(self):
+        # Act / Assert
+        self.assertLess(self.a, self.z)
+
+    def test_compare__le__(self):
+        # Act / Assert
+        self.assertLessEqual(self.a, self.a2)
+        self.assertLessEqual(self.a, self.z)
+
+    def test_compare__gt__(self):
+        # Act / Assert
+        self.assertGreater(self.z, self.a)
+
+    def test_compare__ge__(self):
+        # Act / Assert
+        self.assertGreaterEqual(self.a2, self.a)
+        self.assertGreaterEqual(self.z, self.a)