Ignore `Enum` if it is unavailable (#454)

3 files changed, 42 insertions, 33 deletions

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 9cfed7f..fd90ddd 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -18,6 +18,7 @@ jobs:
           - { python-version: "3.8", session: "py38" }
           - { python-version: "3.7", session: "py37" }
           - { python-version: "3.6", session: "py36" }
+          - { python-version: "2.7", session: "py27" }
 
     steps:
       - name: Check out the repository
@@ -29,6 +30,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: Install tox-setuptools-version
+        if: ${{ matrix.session != 'py27' }}
         run: |
           pip install tox-setuptools-version
 
diff --git a/voluptuous/tests/tests.py b/voluptuous/tests/tests.py
index 049221b..8b95500 100644
--- a/voluptuous/tests/tests.py
+++ b/voluptuous/tests/tests.py
@@ -1,6 +1,9 @@
 import copy
 import collections
-from enum import Enum
+try:
+    from enum import Enum
+except ImportError:
+    Enum = None
 import os
 import sys
 
@@ -1613,38 +1616,39 @@ def test_any_with_discriminant():
     else:
         assert False, "Did not raise correct Invalid"
 
-def test_coerce_enum():
-    """Test Coerce Enum"""
-    class Choice(Enum):
-        Easy = 1
-        Medium = 2
-        Hard = 3
+if Enum:
+    def test_coerce_enum():
+        """Test Coerce Enum"""
+        class Choice(Enum):
+            Easy = 1
+            Medium = 2
+            Hard = 3
 
-    class StringChoice(str, Enum):
-        Easy = "easy"
-        Medium = "medium"
-        Hard = "hard"
+        class StringChoice(str, Enum):
+            Easy = "easy"
+            Medium = "medium"
+            Hard = "hard"
 
-    schema = Schema(Coerce(Choice))
-    string_schema = Schema(Coerce(StringChoice))
+        schema = Schema(Coerce(Choice))
+        string_schema = Schema(Coerce(StringChoice))
 
-    # Valid value
-    assert schema(1) == Choice.Easy
-    assert string_schema("easy") == StringChoice.Easy
+        # Valid value
+        assert schema(1) == Choice.Easy
+        assert string_schema("easy") == StringChoice.Easy
 
-    # Invalid value
-    try:
-        schema(4)
-    except Invalid as e:
-        assert_equal(str(e),
-                     "expected Choice or one of 1, 2, 3")
-    else:
-        assert False, "Did not raise Invalid for String"
+        # Invalid value
+        try:
+            schema(4)
+        except Invalid as e:
+            assert_equal(str(e),
+                        "expected Choice or one of 1, 2, 3")
+        else:
+            assert False, "Did not raise Invalid for String"
 
-    try:
-        string_schema("hello")
-    except Invalid as e:
-        assert_equal(str(e),
-                     "expected StringChoice or one of 'easy', 'medium', 'hard'")
-    else:
-        assert False, "Did not raise Invalid for String"
+        try:
+            string_schema("hello")
+        except Invalid as e:
+            assert_equal(str(e),
+                        "expected StringChoice or one of 'easy', 'medium', 'hard'")
+        else:
+            assert False, "Did not raise Invalid for String"
diff --git a/voluptuous/validators.py b/voluptuous/validators.py
index 109342d..bf1ab06 100644
--- a/voluptuous/validators.py
+++ b/voluptuous/validators.py
@@ -4,7 +4,10 @@ import datetime
 import sys
 from functools import wraps
 from decimal import Decimal, InvalidOperation
-from enum import Enum
+try:
+    from enum import Enum
+except ImportError:
+    Enum = None
 
 from voluptuous.schema_builder import Schema, raises, message
 from voluptuous.error import (MultipleInvalid, CoerceInvalid, TrueInvalid, FalseInvalid, BooleanInvalid, Invalid,
@@ -104,7 +107,7 @@ class Coerce(object):
             return self.type(v)
         except (ValueError, TypeError, InvalidOperation):
             msg = self.msg or ('expected %s' % self.type_name)
-            if not self.msg and issubclass(self.type, Enum):
+            if not self.msg and Enum and issubclass(self.type, Enum):
                 msg += " or one of %s" % str([e.value for e in self.type])[1:-1]
             raise CoerceInvalid(msg)