Improve "Unexpected input: '{'" error message

Signed-off-by: Ben Sherman <[email protected]>

modules/nextflow/src/main/groovy/nextflow/script/ScriptParser.groovy

@@ -184,6 +184,9 @@ class ScriptParser {
             msg = msg != 'startup failed' ? msg : header
             msg = msg.replaceAll(/startup failed:\n/,'')
             msg = msg.replaceAll(~/$clazzName(: \d+:\b*)?/, header+'\n- cause:')
+            if( msg.contains "Unexpected input: '{'" ) {
+                msg += "\nNOTE: If this is the beginning of a process or workflow, there may be a syntax error in the body, such as a missing or extra comma, for which a more specific error message could not be produced."
+            }
             throw new ScriptCompilationException(msg, e)
         }
     }