Diagnostics for GHFileNotFoundException from retrieve

[jglick]

jenkinsci/github-label-filter-plugin#4 got as far as printing

Reason: org.kohsuke.github.GHFileNotFoundException: https://api.github.com/repos/…/…/issues/… {"message":"Resource not accessible by integration","documentation_url":"https://docs.github.com/rest/reference/issues#get-an-issue"}

CC @jvz

[jglick]

Indeed improves diagnosis:

  Error while processing pull request …
java.io.FileNotFoundException: https://api.github.com/repos/…/…/issues/…
	at org.kohsuke.github.extras.okhttp3.ObsoleteUrlFactory$OkHttpURLConnection.getInputStream(ObsoleteUrlFactory.java:488)
	at org.kohsuke.github.extras.okhttp3.ObsoleteUrlFactory$DelegatingHttpsURLConnection.getInputStream(ObsoleteUrlFactory.java:1201)
	at org.kohsuke.github.GitHubHttpUrlConnectionClient$HttpURLConnectionResponseInfo.bodyStream(GitHubHttpUrlConnectionClient.java:197)
	at org.kohsuke.github.GitHubResponse$ResponseInfo.getBodyAsString(GitHubResponse.java:326)
	at org.kohsuke.github.GitHubResponse.parseBody(GitHubResponse.java:120)
	at org.kohsuke.github.Requester.lambda$fetchInto$2(Requester.java:89)
	at org.kohsuke.github.GitHubClient.createResponse(GitHubClient.java:461)
	at org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:412)
Caused: org.kohsuke.github.GHFileNotFoundException: https://api.github.com/repos/…/…/issues/… {"message":"Resource not accessible by integration","documentation_url":"https://docs.github.com/rest/reference/issues#get-an-issue"}
	at org.kohsuke.github.GitHubClient.interpretApiError(GitHubClient.java:492)
	at org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:420)
	at org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:363)
	at org.kohsuke.github.Requester.fetchInto(Requester.java:89)
	at org.kohsuke.github.GHPullRequest.fetchIssue(GHPullRequest.java:631)
	at org.kohsuke.github.GHPullRequest.getLabels(GHPullRequest.java:182)
	at org.jenkinsci.plugins.github.label.filter.BaseGithubExtendedFilterTrait.getPullRequestLabels(BaseGithubExtendedFilterTrait.java:117)
	at org.jenkinsci.plugins.github.label.filter.PullRequestLabelsMatchAllFilterTrait$1.isExcluded(PullRequestLabelsMatchAllFilterTrait.java:60)
	at jenkins.scm.api.trait.SCMSourceRequest.isExcluded(SCMSourceRequest.java:196)
	at jenkins.scm.api.trait.SCMSourceRequest.process(SCMSourceRequest.java:333)
	at org.jenkinsci.plugins.github_branch_source.GitHubSCMSource.retrievePullRequest(GitHubSCMSource.java:1179)
	at org.jenkinsci.plugins.github_branch_source.GitHubSCMSource.retrieve(GitHubSCMSource.java:1038)
	at jenkins.scm.api.SCMSource._retrieve(SCMSource.java:373)
	at jenkins.scm.api.SCMSource.fetch(SCMSource.java:327)
	at jenkins.branch.MultiBranchProjectFactory$BySCMSourceCriteria.recognizes(MultiBranchProjectFactory.java:261)
	at jenkins.branch.OrganizationFolder$SCMSourceObserverImpl$1.recognizes(OrganizationFolder.java:1468)
	at jenkins.branch.OrganizationFolder$SCMSourceObserverImpl$1.complete(OrganizationFolder.java:1483)
	at jenkins.scm.api.trait.SCMNavigatorRequest.process(SCMNavigatorRequest.java:254)
	at jenkins.scm.api.trait.SCMNavigatorRequest.process(SCMNavigatorRequest.java:204)
	at org.jenkinsci.plugins.github_branch_source.GitHubSCMNavigator.visitSources(GitHubSCMNavigator.java:1024)
	at jenkins.branch.OrganizationFolder.computeChildren(OrganizationFolder.java:542)
	at …