title: The blob supplied is not valid when deploying data factory pipeline with custom .net activity
body: <p>I've been getting this "useful" error message when deploying an experimental data factory pipeline that has a DotNetActivity within it.</p>
  
  <blockquote>
    <p>Entity provisioning failed: The blob supplied is not valid. Blob:
    customactivity/package.zip. Error code: . Error message: .</p>
  </blockquote>
  
  <p>I've been reading trouble shooting tips and double checking connection strings, but to no avail.</p>