Build fails with error NU1510: Warning As Error: PackageReference System.Text.Json will not be pruned

[frankbuckley]

Following (I think) the guidelines for building Microsoft.Data.SqlClient, when I execute msbuild I get:

Build FAILED.

"V:\dev\frankbuckley\SqlClient\build.proj" (Restore target) (1) ->
"V:\dev\frankbuckley\SqlClient\src\Microsoft.Data.SqlClient\netcore\ref\Microsoft.Data.SqlClient.csproj" (restore target) (4) ->
(Restore target) ->
  V:\dev\frankbuckley\SqlClient\src\Microsoft.Data.SqlClient\netcore\ref\Microsoft.Data.SqlClient.csproj : error NU1510: Warning As Error: PackageReference System.Text.Json will not be pruned. Consider removing this package from your dependencies, as it is likely unnecessary.
  V:\dev\frankbuckley\SqlClient\src\Microsoft.Data.SqlClient\netcore\ref\Microsoft.Data.SqlClient.csproj : error NU1510: Warning As Error: PackageReference System.Text.Json will not be pruned. Consider removing this package from your dependencies, as it is likely unnecessary.


"V:\dev\frankbuckley\SqlClient\build.proj" (Restore target) (1) ->
"V:\dev\frankbuckley\SqlClient\src\Microsoft.Data.SqlClient\netcore\src\Microsoft.Data.SqlClient.csproj" (restore target) (5) ->
  V:\dev\frankbuckley\SqlClient\src\Microsoft.Data.SqlClient\netcore\src\Microsoft.Data.SqlClient.csproj : error NU1510: Warning As Error: PackageReference System.Text.Json will not be pruned. Consider removing this package from your dependencies, as it is likely unnecessary.
  V:\dev\frankbuckley\SqlClient\src\Microsoft.Data.SqlClient\netcore\src\Microsoft.Data.SqlClient.csproj : error NU1510: Warning As Error: PackageReference System.Text.Json will not be pruned. Consider removing this package from your dependencies, as it is likely unnecessary.

    0 Warning(s)
    4 Error(s)

Have I missed something?