I recently upgraded to 7.0.20 and started seeing this issue on our master branch builds of Neovim:

20:48:42,707 INFO - Checking step execute condition...
20:48:42,707 INFO - Step execute condition satisfied, executing...
20:48:42,862 INFO - Executing pre-execute action...
20:48:42,862 INFO - Running step...
20:48:42,862 INFO - Checking out revision '3b45f676c0f07aa2826f191f555ba0d5f53e6d7c' of repository 'github'...
20:48:43,174 INFO - Executing post-execute action...
20:48:43,174 ERROR - Step 'master>buildall>build-node?testNode=macosx-64>checkout' is failed.
    java.lang.RuntimeException: org.eclipse.egit.github.core.client.RequestException: Not Found (404)
        at com.google.common.base.Throwables.propagate(Throwables.java:160)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository.onBuildStart(GitHubRepository.java:74)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository.checkoutByRevision(GitHubRepository.java:65)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e.CGLIB$checkoutByRevision$9(<generated>)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e$$FastClassByCGLIB$$3c8903c5.invoke(<generated>)
        at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:215)
        at com.pmease.quickbuild.DefaultScriptEngine$Interpolator.intercept(DefaultScriptEngine.java:261)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e.checkoutByRevision(<generated>)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository.checkoutByRevision(GitHubRepository.java:48)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e.CGLIB$checkoutByRevision$8(<generated>)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e$$FastClassByCGLIB$$3c8903c5.invoke(<generated>)
        at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:215)
        at com.pmease.quickbuild.DefaultScriptEngine$Interpolator.intercept(DefaultScriptEngine.java:261)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e.checkoutByRevision(<generated>)
        at com.pmease.quickbuild.repositorysupport.Repository.checkout(Repository.java:228)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e.CGLIB$checkout$104(<generated>)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e$$FastClassByCGLIB$$3c8903c5.invoke(<generated>)
        at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:215)
        at com.pmease.quickbuild.DefaultScriptEngine$Interpolator.intercept(DefaultScriptEngine.java:261)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository$$EnhancerByCGLIB$$b0f324e.checkout(<generated>)
        at com.pmease.quickbuild.repositorysupport.CheckoutStep.run(CheckoutStep.java:71)
        at com.pmease.quickbuild.repositorysupport.CheckoutStep$$EnhancerByCGLIB$$82062b73.CGLIB$run$0(<generated>)
        at com.pmease.quickbuild.repositorysupport.CheckoutStep$$EnhancerByCGLIB$$82062b73$$FastClassByCGLIB$$ff934e00.invoke(<generated>)
        at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:215)
        at com.pmease.quickbuild.DefaultScriptEngine$Interpolator.intercept(DefaultScriptEngine.java:261)
        at com.pmease.quickbuild.repositorysupport.CheckoutStep$$EnhancerByCGLIB$$82062b73.run(<generated>)
        at com.pmease.quickbuild.stepsupport.Step.doExecute(Step.java:619)
        at com.pmease.quickbuild.stepsupport.Step.execute(Step.java:521)
        at com.pmease.quickbuild.stepsupport.StepExecutionJob.executeStepAwareJob(StepExecutionJob.java:31)
        at com.pmease.quickbuild.stepsupport.StepAwareJob.executeBuildAwareJob(StepAwareJob.java:45)
        at com.pmease.quickbuild.BuildAwareJob.execute(BuildAwareJob.java:60)
        at com.pmease.quickbuild.grid.GridJob.run(GridJob.java:106)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
    Caused by: org.eclipse.egit.github.core.client.RequestException: Not Found (404)
        at org.eclipse.egit.github.core.client.GitHubClient.createException(GitHubClient.java:583)
        at org.eclipse.egit.github.core.client.GitHubClient.sendJson(GitHubClient.java:674)
        at org.eclipse.egit.github.core.client.GitHubClient.post(GitHubClient.java:788)
        at org.eclipse.egit.github.core.service.CommitService.createStatus(CommitService.java:428)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository.updateCommitStatus(GitHubRepository.java:200)
        at com.pmease.quickbuild.plugin.scm.github.GitHubRepository.onBuildStart(GitHubRepository.java:71)
        ... 35 more

I'm not quite sure what it's trying to tell me, but this used to work just fine previously.