How to reproduce:
1. Create a new Unity 3D project
2. Download Unity's SRP from GitHub (For example: https://github.com/Unity-Technologies/Graphics/archive/v7.5.1.zip)
3. Go to the Package Manager -> Add package from disk...
4. From downloaded Unity's SRP select com.unity.render-pipelines.core -> package.json
5. Wait for the package to import

Expected result: Package imports with no errors
Actual result: Console fills up with errors

Reproducible with: 7.5.1(2019.4.15f1), 9.0.0-preview.79 (2020.1.15f1), 10.2.0 (2020.2.0b13), 11.0.0 (2021.1.0a7)
Could not test with: 2018.4.29f1 (no Core RP Library)

Errors:
/Users/UserName/Downloads/Graphics/com.unity.render-pipelines.core/Editor/ShaderGenerator/CSharpToHLSL.cs(3,7): error CS0246: The type or namespace name 'ICSharpCode' could not be found (are you missing a using directive or an assembly reference?)

Could not create asset from Packages/com.unity.render-pipelines.core/Editor/Lighting/Icons/IESProfile.png: File could not be read