Fix parse_key_from_error_msg to not error out on non-string keys

Signed-off-by: Joffrey F <joffrey@docker.com>

compose/config/validation.py

@@ -330,7 +330,10 @@ def handle_generic_error(error, path):
 
 
 def parse_key_from_error_msg(error):
+    try:
         return error.message.split("'")[1]
+    except IndexError:
+        return error.message.split('(')[1].split(' ')[0].strip("'")
 
 
 def path_string(path):

tests/unit/config/config_test.py

@@ -613,6 +613,19 @@ class ConfigTest(unittest.TestCase):
             excinfo.exconly()
         )
 
+    def test_config_integer_service_property_raise_validation_error(self):
+        with pytest.raises(ConfigurationError) as excinfo:
+            config.load(
+                build_config_details({
+                    'version': '2.1',
+                    'services': {'foobar': {'image': 'busybox', 1234: 'hah'}}
+                }, 'working_dir', 'filename.yml')
+            )
+
+        assert (
+            "Unsupported config option for services.foobar: '1234'" in excinfo.exconly()
+        )
+
     def test_config_invalid_service_name_raise_validation_error(self):
         with pytest.raises(ConfigurationError) as excinfo:
             config.load(