Improve local exec workdir validation

Signed-off-by: Paolo Di Tommaso <paolo.ditommaso@gmail.com>

modules/nextflow/src/main/groovy/nextflow/executor/local/LocalExecutor.groovy

@@ -21,8 +21,10 @@ import java.nio.file.FileSystems
 
 import groovy.transform.CompileStatic
 import groovy.util.logging.Slf4j
+import nextflow.exception.ProcessUnrecoverableException
 import nextflow.executor.Executor
 import nextflow.executor.SupportedScriptTypes
+import nextflow.extension.FilesEx
 import nextflow.fusion.FusionHelper
 import nextflow.processor.LocalPollingMonitor
 import nextflow.processor.TaskHandler
@@ -61,9 +63,11 @@ class LocalExecutor extends Executor {
     @Override
     protected void register() {
         super.register()
-        if( workDir.fileSystem != FileSystems.default && !isFusionEnabled() ) {
-            log.warn "Local executor only supports default file system (unless Fusion is enabled) -- Check work directory: ${getWorkDir().toUriString()}"
-        }
+        final remoteFs = workDir.fileSystem!=FileSystems.default
+        if(  isFusionEnabled() && !remoteFs )
+            throw new ProcessUnrecoverableException("Fusion file system requires the use of a S3-compatible object storage — offending work directory path: ${FilesEx.toUriString(workDir)}")
+        if( remoteFs && !isFusionEnabled())
+            throw new ProcessUnrecoverableException("Local executor requires the use of POSIX compatible file system — offending work directory path: ${FilesEx.toUriString(workDir)}")
     }
 
     @Override