Fix argument order

elm_package.py

@@ -41,7 +41,7 @@ def sync_deps(from_deps, to_deps):
         elif to_deps[package_name] != package_version:
             result[package_name] = package_version
 
-            messages.append('Changing {package_name} from version {package_version} to {other_package_version}'.format(
+            messages.append('Changing {package_name} from version {other_package_version} to {package_version}'.format(
                 package_version=package_version, package_name=package_name,
                 other_package_version=to_deps[package_name])
             )

tests/test_elm_package.py

@@ -0,0 +1,10 @@
+import elm_package
+
+
+def test_sync_deps_messages_when_version_is_changed():
+    from_deps = {'core': '1.0.0'}
+    to_deps = {'core': '0.1.0'}
+
+    messages, new_deps = elm_package.sync_deps(from_deps, to_deps)
+    assert len(messages) == 1
+    assert '0.1.0 to 1.0.0' in messages[0]