"Not Found" displayed when clicking on PR link in review

[meaghanlewis]

Hello! Please read the contributing guidelines before submitting an issue regarding the GitHub Extension for Visual Studio.

• GitHub Extension for Visual Studio version: VS2015
• Visual Studio version: 2.5.2.2566

What happened
In VS2015 specifically when I click on a PR number link while doing a review I just see "Not Found". This fork can be used to repro: https://github.com/meaghanlewis-tester/my-first-repo

Logs

Octokit.NotFoundException: Not Found
   at Octokit.Connection.HandleErrors(IResponse response) in C:\projects\visualstudio\submodules\octokit.net\Octokit\Http\Connection.cs:line 652
   at Octokit.Connection.<RunRequest>d__57.MoveNext() in C:\projects\visualstudio\submodules\octokit.net\Octokit\Http\Connection.cs:line 633
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Octokit.Connection.<Run>d__56`1.MoveNext() in C:\projects\visualstudio\submodules\octokit.net\Octokit\Http\Connection.cs:line 618
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Octokit.ApiConnection.<Get>d__8`1.MoveNext() in C:\projects\visualstudio\submodules\octokit.net\Octokit\Http\ApiConnection.cs:line 0
--- End of stack trace from previous location where exception was thrown ---
   at System.Reactive.PlatformServices.ExceptionServicesImpl.Rethrow(Exception exception)
   at System.Reactive.ExceptionHelpers.ThrowIfNotNull(Exception exception)
   at System.Reactive.Subjects.AsyncSubject`1.GetResult()
   at GitHub.ViewModels.GitHubPane.PullRequestDetailViewModel.<Refresh>d__101.MoveNext() in C:\projects\visualstudio\src\GitHub.App\ViewModels\GitHubPane\PullRequestDetailViewModel.cs:line 482
{"message":"Not Found","documentation_url":"https://developer.github.com/v3/pulls/#get-a-single-pull-request"}
2018-05-17 13:00:31.217 [01536] EROR [01] PullRequestDetailViewModel Error loading pull request githubtestorganization/TestWebAppProject/24 from GitHub
Octokit.NotFoundException: Not Found
   at Octokit.Connection.HandleErrors(IResponse response) in C:\projects\visualstudio\submodules\octokit.net\Octokit\Http\Connection.cs:line 652
   at Octokit.Connection.<RunRequest>d__57.MoveNext() in C:\projects\visualstudio\submodules\octokit.net\Octokit\Http\Connection.cs:line 633
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Octokit.Connection.<Run>d__56`1.MoveNext() in C:\projects\visualstudio\submodules\octokit.net\Octokit\Http\Connection.cs:line 618
--- End of stack trace from previous location where exception was thrown ---
   at System.Reactive.PlatformServices.ExceptionServicesImpl.Rethrow(Exception exception)
   at System.Reactive.ExceptionHelpers.ThrowIfNotNull(Exception exception)
   at System.Reactive.Subjects.AsyncSubject`1.GetResult()
   at GitHub.ViewModels.GitHubPane.PullRequestDetailViewModel.<Refresh>d__101.MoveNext() in C:\projects\visualstudio\src\GitHub.App\ViewModels\GitHubPane\PullRequestDetailViewModel.cs:line 482
{"message":"Not Found","documentation_url":"https://developer.github.com/v3/pulls/#list-pull-requests-files"}```

[StanleyGoldman]

I'm testing locally and I'm not able to make this happen.
I think this might have been fixed already.

[meaghanlewis]

I'm testing this again and notice a different issue than before actually

It looks like there might be 2 problems:
1. Can't open PR link from upstream

It looks like the link is trying to open up: meaghanlewis/my-first-repo/4 instead of: meaghanlewis-tester/my-first-repo/4

2. Clicking on the View on GitHub button in this error view tries open up a link to the wrong location and fails.

For instance, in the example above, clicking the View on GitHub button opens the browser to: https://github.com/meaghanlewis/my-first-repo/issues/4 instead of meaghanlewis-tester/my-first-repo#4

Log:
2018-08-06 10:26:52.074 [09120] INFO [14] GitHubPackage Initializing GitHub Extension v2.5.4.3431 in Microsoft Visual Studio 2015 (14.0.25420.1) 2018-08-06 10:31:52.775 [09120] EROR [01] PullRequestDetailViewModel Error loading pull request meaghanlewis/my-first-repo/4 from GitHub System.NullReferenceException: Object reference not set to an instance of an object. at GitHub.ViewModels.GitHubPane.PullRequestDetailViewModel.<Refresh>d__106.MoveNext() in C:\projects\visualstudio\src\GitHub.App\ViewModels\GitHubPane\PullRequestDetailViewModel.cs:line 0 2018-08-06 10:31:53.503 [09120] EROR [01] PullRequestDetailViewModel Error loading pull request meaghanlewis/my-first-repo/4 from GitHub