Handle various errors from doValidateRepositoryUrlAndCredentials

[jglick]

I got an Angry Jenkins while trying to validate a connection to a GitHub Enterprise server behind a VPN. System log said:

java.net.SocketTimeoutException: Connect timed out
	at java.base/sun.nio.ch.NioSocketImpl.timedFinishConnect(NioSocketImpl.java:551)
	at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:602)
	at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:327)
	at java.base/java.net.Socket.connect(Socket.java:633)
	at PluginClassLoader for okhttp-api//okhttp3.internal.platform.Platform.connectSocket(Platform.kt:128)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.RealConnection.connectSocket(RealConnection.kt:295)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.RealConnection.connect(RealConnection.kt:207)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.ExchangeFinder.findConnection(ExchangeFinder.kt:226)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.ExchangeFinder.findHealthyConnection(ExchangeFinder.kt:106)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.ExchangeFinder.find(ExchangeFinder.kt:74)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.RealCall.initExchange$okhttp(RealCall.kt:255)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.kt:32)
	at PluginClassLoader for okhttp-api//okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:109)
	at PluginClassLoader for okhttp-api//okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.kt:95)
	at PluginClassLoader for okhttp-api//okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:109)
	at PluginClassLoader for okhttp-api//okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.kt:83)
	at PluginClassLoader for okhttp-api//okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:109)
	at PluginClassLoader for okhttp-api//okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.kt:76)
	at PluginClassLoader for okhttp-api//okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:109)
	at PluginClassLoader for github-api//org.kohsuke.github.extras.okhttp3.ObsoleteUrlFactory$UnexpectedException.lambda$static$0(ObsoleteUrlFactory.java:1364)
	at PluginClassLoader for okhttp-api//okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:109)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.RealCall.getResponseWithInterceptorChain$okhttp(RealCall.kt:201)
	at PluginClassLoader for okhttp-api//okhttp3.internal.connection.RealCall.execute(RealCall.kt:154)
	at PluginClassLoader for github-api//org.kohsuke.github.extras.okhttp3.ObsoleteUrlFactory$OkHttpURLConnection.getResponse(ObsoleteUrlFactory.java:670)
	at PluginClassLoader for github-api//org.kohsuke.github.extras.okhttp3.ObsoleteUrlFactory$OkHttpURLConnection.getResponseCode(ObsoleteUrlFactory.java:701)
	at PluginClassLoader for github-api//org.kohsuke.github.extras.okhttp3.ObsoleteUrlFactory$DelegatingHttpsURLConnection.getResponseCode(ObsoleteUrlFactory.java:1063)
	at PluginClassLoader for github-api//org.kohsuke.github.internal.GitHubConnectorHttpConnectorAdapter.send(GitHubConnectorHttpConnectorAdapter.java:87)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:461)
Caused: org.kohsuke.github.HttpException: Server returned HTTP response code: -1, message: 'null' for URL: https://github.example.com/api/v3/app
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.interpretApiError(GitHubClient.java:743)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:478)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:427)
	at PluginClassLoader for github-api//org.kohsuke.github.Requester.fetch(Requester.java:85)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHub.getApp(GitHub.java:1189)
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.GitHubAppCredentials.generateAppInstallationToken(GitHubAppCredentials.java:218)
Caused: java.lang.IllegalArgumentException: Couldn't authenticate with GitHub app ID 1234
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.GitHubAppCredentials.generateAppInstallationToken(GitHubAppCredentials.java:220)
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.GitHubAppCredentials.getToken(GitHubAppCredentials.java:295)
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.GitHubAppCredentials$CredentialsTokenProvider.getEncodedAuthorization(GitHubAppCredentials.java:199)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.prepareConnectorRequest(GitHubClient.java:616)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:455)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.fetch(GitHubClient.java:159)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHubClient.checkApiUrlValidity(GitHubClient.java:390)
	at PluginClassLoader for github-api//org.kohsuke.github.GitHub.checkApiUrlValidity(GitHub.java:1321)
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.ApiRateLimitChecker.verifyConnection(ApiRateLimitChecker.java:194)
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.Connector$GitHubConnection.verifyConnection(Connector.java:722)
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.Connector.connect(Connector.java:419)
	at PluginClassLoader for github-branch-source//org.jenkinsci.plugins.github_branch_source.GitHubSCMSource$DescriptorImpl.doValidateRepositoryUrlAndCredentials(GitHubSCMSource.java:2143)

Maybe generateAppInstallationToken should be allowed to throw IOException, but anyway it seems that if Connector.connect fails for any reason, that is presumably something you want displayed in the output of the validation button, not sent to the system log.