How to reproduce:

1. Create new Unity Project
2. In Context menu select Window > Package Manager
3. In package manager windows click on plus icon
4. In dropdown select 'install package from git URL...'
5. Enter this link 'https://github.com/Unity-Technologies/Graphics.git?path=com.unity.postprocessing' and press Install
6. Wait for install to complete and check console

{code:java}
System.ArgumentException: Type provided must be an Enum.
Parameter name: enumType
at System.RuntimeType.GetEnumValues () [0x00012] in <e1eafe244ab8433bb57e5e98843c8df1>:0
at System.Enum.GetValues (System.Type enumType) [0x00014] in <e1eafe244ab8433bb57e5e98843c8df1>:0
at UnityEditor.Rendering.PostProcessing.DefineSetter..cctor () [0x00000] in /home/bokken/My project (5)/Library/PackageCache/com.unity.postprocessing@b336715bc7/PostProcessing/Editor/Tools/DefineSetter.cs:17
UnityEditor.EditorAssemblies:ProcessInitializeOnLoadAttributes (System.Type[]) (at /home/bokken/buildslave/unity/build/Editor/Mono/EditorAssemblies.cs:123)
{code}

Expected results: No errors in console.
Actual results: Errors are thrown in the Console window

Notes:
- Tested on Win11, Ubuntu 18.
- Not reproducible with version 3.2.2.
- Also tried same package install from disk and got the same error