stack trace retrieving subnets

I assume this is something wrong with my configuration, but I'm not sure what. The build completed successfully, everything seemed fine. The Jenkins web server did end up delivering 503 pages about twenty hours later, and there were no other indicators in the logs of why *that* might be the case, but a restart cleared it.

Jenkins is 2.204.1, GCE plugin is 4.2.0.

```
2020-02-27 23:00:43.067+0000 [id=44] INFO c.g.j.p.c.ComputeEngineCloud#provision: Provisioning node from configs [com.google.jenkins.plugins.computeengine.InstanceConfiguration@921cba] for excess workload of 1 units of label 'wrt'
2020-02-27 23:00:43.358+0000 [id=44] INFO c.g.j.p.c.ComputeEngineCloud#availableNodeCapacity: Found capacity for 2 nodes in cloud Jenkins GCE
2020-02-27 23:00:45.377+0000 [id=44] INFO c.g.j.p.c.InstanceConfiguration#provision: Sent insert request for instance configuration [Jenkins build node for rWRT]
2020-02-27 23:00:45.379+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineComputerLauncher#launch: Launch will wait 120000 for operation operation-1582844443818-59f96b0cefbe7-7fdbe62f-76e0178e to complete...
2020-02-27 23:00:45.397+0000 [id=44] INFO h.s.NodeProvisioner$StandardStrategyImpl#apply: Started provisioning jenkins-build-wrt-twbh3l from gce-Jenkins GCE with 1 executors. Remaining excess workload: 0
2020-02-27 23:00:45.398+0000 [id=82863] INFO c.g.j.p.c.ComputeEngineCloud#lambda$getPlannedNodeFuture$0: Waiting 120000ms for node jenkins-build-wrt-twbh3l to connect
2020-02-27 23:01:11.623+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Launching instance: jenkins-build-wrt-twbh3l
2020-02-27 23:01:11.623+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: bootstrap
2020-02-27 23:01:11.623+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Getting keypair...
2020-02-27 23:01:11.623+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Using autogenerated keypair
2020-02-27 23:01:11.624+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Authenticating as jenkins
2020-02-27 23:01:11.811+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Connecting to 10.138.15.210 on port 22, with timeout 10000.
2020-02-27 23:01:19.323+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Connected via SSH.
2020-02-27 23:01:19.382+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Verifying: java -fullversion
2020-02-27 23:01:19.508+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Copying agent.jar to: /tmp
2020-02-27 23:01:19.537+0000 [id=82865] INFO c.g.j.p.c.ComputeEngineCloud#log: Launching Jenkins agent via plugin SSH: java -jar /tmp/agent.jar
2020-02-27 23:01:22.945+0000 [id=82863] INFO c.g.j.p.c.ComputeEngineCloud#lambda$getPlannedNodeFuture$0: 37548ms elapsed waiting for node jenkins-build-wrt-twbh3l to connect
2020-02-27 23:08:32.709+0000 [id=82735] SEVERE c.g.j.p.c.AutofilledNetworkConfiguration$DescriptorImpl#doFillSubnetworkItems: Error retrieving subnetworks
java.lang.IllegalArgumentException
at com.google.common.base.Preconditions.checkArgument(Preconditions.java:72)
at com.google.cloud.graphite.platforms.plugin.client.ComputeClient.listSubnetworks(ComputeClient.java:277)
at com.google.jenkins.plugins.computeengine.AutofilledNetworkConfiguration$DescriptorImpl.doFillSubnetworkItems(AutofilledNetworkConfiguration.java:103)
at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:396)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:408)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:212)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:145)
at org.kohsuke.stapler.MetaClass$11.doDispatch(MetaClass.java:535)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:747)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:878)
at org.kohsuke.stapler.MetaClass$4.doDispatch(MetaClass.java:280)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:747)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:878)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:676)
at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:873)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1623)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:154)
at org.jenkinsci.plugins.ssegateway.Endpoint$SSEListenChannelFilter.doFilter(Endpoint.java:246)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151)
at jenkins.security.ResourceDomainFilter.doFilter(ResourceDomainFilter.java:76)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151)
at io.jenkins.blueocean.ResourceCacheControl.doFilter(ResourceCacheControl.java:134)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151)
at io.jenkins.blueocean.auth.jwt.impl.JwtAuthenticationFilter.doFilter(JwtAuthenticationFilter.java:61)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151)
at org.jenkinsci.plugins.modernstatus.ModernStatusFilter.doFilter(ModernStatusFilter.java:52)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151)
at jenkins.telemetry.impl.UserLanguages$AcceptLanguageFilter.doFilter(UserLanguages.java:128)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:157)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:99)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:118)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:93)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:90)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:540)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1700)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1667)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.Server.handle(Server.java:505)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:333)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:310)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:698)
at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:804)
at java.lang.Thread.run(Thread.java:748)
```