Add value for NU1507 warning string format item

[tlmii]

Bug

Fixes: NuGet/Home#11709

Regression? Last working version: Not a regression

Description

It looks like #4505 missed calling string.Format and passing the value when the warning text was changed to include a format item for the number of sources. This PR corrects that.

Note that this doesn't address all of the points in NuGet/Home#11709, just the main one of the missing value, so I don't think completing this PR should close that one.

PR Checklist

• PR has a meaningful title

• PR has a linked issue.

• Described changes

• Tests

  • Automated tests added
  • OR
  • Test exception
  • OR
  • N/A

• Documentation

  • Documentation PR or issue filled
  • OR
  • N/A

[jeffkl]

Thanks @tlmii, I've pushed an update to the unit test to your branch as well

[nkolev92]

@jeffkl
Do you think adding the names of the sources would be helpful?

There are many ways to add sources, NuGet.Config, RestoreSources, RestoreAdditionalProjectSources etc.
It can be difficult to find the sources sometimes and having the names would help.

[nkolev92]

should we be considering this change for 17.2 as well? @jeffkl

[tlmii]

Thanks @tlmii, I've pushed an update to the unit test to your branch as well

Thanks @jeffkl . I wasn't sure if it was safe to do the string check that way (localization, etc) but good to see we can have that check in there.

[jeffkl]

The plan is to merge this into dev and cherry-pick for 17.2 so we can take it to shiproom

[jeffkl]

Can you please make sure the issue is created. @jeffkl

NuGet/Home#11715