Execution hangs when the amount of requested resources exceed the available ones

[pditommaso]

To replicate the issue specify a stupidly big number of cpus eg 200 by using the local executor.

The execution hangs and following error stack trace is printed:

 Submitted process > fastqc (FASTQC on SRR3192434)
Exception in thread "Task submitter" nextflow.exception.ProcessNotRecoverableException: Process requirement exceed available memory -- req: 16 GB; avail: 15.7 GB
	at nextflow.processor.LocalPollingMonitor.canSubmit(LocalPollingMonitor.groovy:179)
	at nextflow.processor.TaskPollingMonitor.submitPendingTasks(TaskPollingMonitor.groovy:455)
	at nextflow.processor.TaskPollingMonitor.submitLoop(TaskPollingMonitor.groovy:311)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
	at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
	at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1213)
	at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1080)
	at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1022)
	at groovy.lang.Closure.call(Closure.java:414)
	at groovy.lang.Closure.call(Closure.java:408)
	at groovy.lang.Closure.run(Closure.java:495)
	at java.lang.Thread.run(Thread.java:745)