Remove http client leak

[i386]

The ClosableHttpClient is never released correctly if an exception occurs. This could lead to leaked unclosed connections to Github.

Note: this PR depends on #61 and needs a rebase when it is merged. As such it contains all the improvements in #62 and this PR.

PTAL @samrocketman

[i386]

This method replaces the code above for resolving the code to an accessToken.

[samrocketman]

Please rebase this. #61 has been merged.

[samrocketman]

@i386 I'm also having trouble with the pom2.3 branch building with Java 1.8. Do you mind taking a look at it as well? The reason to migrate to pom2.3 is releasing via HTTPS.

[i386]

@samrocketman I've rebased and pushed - this PR is ready for review.

Strange that you are having issues on Java 8 as thats what I've been building it with locally. What error are you seeing?

[samrocketman]

I'll start reviewing this PR and merge if I think it's ready.

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in reply to:

Strange that you are having issues on Java 8 as thats what I've been building it with locally. What error are you seeing?

I'm using:

• Oracle java version "1.8.0_91".
• Apache Maven 3.3.9

On the pom2.3 branch I get errors like:

testCanReadAndBuildOrgRepositoryICollaborateOn(org.jenkinsci.plugins.GithubRequireOrganizationMembershipACLTest)  Time elapsed: 0.003 sec  <<< ERROR!
java.lang.IllegalStateException: attempt to register a second Permission for hudson.model.Item.ViewStatus
        at hudson.security.PermissionGroup.add(PermissionGroup.java:72)
        at hudson.security.Permission.<init>(Permission.java:162)
        at hudson.security.Permission.<init>(Permission.java:168)
        at org.jenkinsci.plugins.GithubRequireOrganizationMembershipACLTest.<init>(GithubRequireOrganizationMembershipACLTest.java:95)

So I guess it's not specifically related to Java 8 in this case but due to upgrading the base version of Jenkins the plugin is built against. I'm having trouble upgrading to the new Jenkins pom.xml format. You can learn about what I tried in the commit message 6a0aee1. There's also links I added as comments inline in the diff.

If you figure it out feel free to cherry-pick my commit and propose fixes in a new PR. Thanks for taking the time to entertain my request.

[samrocketman]

Tested OK.