This version of Unity is unsupported.
Mono Cecil
Package Validation Suite

Package Development

com.unity.upm.develop preview 

Description

Installs the UPM package development extension. Author new UPM packages and manage them with the new In-Development mode in the Package Manager UI. Publish your packages to a local file, scoped registry or Asset Store

Version information

Experimental or in preview for Unity

These package versions might not be safe to use in production with Unity version 2019.4:

Documentation location: State Versions available:
com.unity.upm.develop@0.1 preview 0.1.1-preview, 0.1.2-preview
Mono Cecil
Package Validation Suite