Model is stuck in 'modelchecking' state.

Fixes Github issue #143
https://github.com/tlaplus/tlaplus/issues/143

[Bug][Toolbox]

tlatools/src/tla2sany/modanalyzer/ParseUnit.java

@@ -255,10 +255,10 @@ public class ParseUnit {
         ***********************************************************************/
         if (ToolIO.getMode() == ToolIO.SYSTEM)
         {
-			ToolIO.out.printf("Parsing file %s\n", absoluteResolvedPath);
+			ToolIO.out.println(String.format("Parsing file %s\n", absoluteResolvedPath));
         } else
         {
-            ToolIO.out.printf("Parsing module %s in file %s\n", nis.getModuleName(), absoluteResolvedPath);
+            ToolIO.out.println(String.format("Parsing module %s in file %s\n", nis.getModuleName(), absoluteResolvedPath));
         }
 
         boolean parseSuccess; 

tlatools/src/util/ToolIO.java

@@ -5,6 +5,7 @@ import java.io.PrintStream;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Locale;
 
 import tla2sany.semantic.SemanticNode;
 
@@ -87,7 +88,7 @@ public class ToolIO
      * List of semantic nodes which are used by tools
      * @see ToolIO#registerSemanticNode() 
      */
-    private static List semanticNodes = new LinkedList();
+    private static List<SemanticNode> semanticNodes = new LinkedList<>();
 
     /**
      * The current sequence of messages is messages[0] ...                  
@@ -253,10 +254,10 @@ public class ToolIO
      */
     public static void cleanToolObjects(int toolId)
     {
-        Iterator iter = semanticNodes.iterator();
+        Iterator<SemanticNode> iter = semanticNodes.iterator();
         while(iter.hasNext())
         {
-            SemanticNode node = (SemanticNode) iter.next();
+            SemanticNode node = iter.next();
             node.setToolObject(toolId, null);
         }
     }
@@ -266,7 +267,7 @@ public class ToolIO
      */
     public static void unregisterSemanticNodes()
     {
-        semanticNodes = new LinkedList();
+        semanticNodes = new LinkedList<SemanticNode>();
     }
 
 } // class ToolIO
@@ -283,6 +284,26 @@ class ToolPrintStream extends PrintStream
         ToolIO.err = this;
     }
     
+    /* (non-Javadoc)
+     * @see java.io.PrintStream#printf(java.lang.String, java.lang.Object[])
+     */
+    @Override
+	public PrintStream printf(String format, Object... args) {
+		// See special logic in println. If super.printf(...) gets used, Toolbox
+		// functionality breaks.
+    	throw new UnsupportedOperationException("use println instead");
+	}
+
+	/* (non-Javadoc)
+	 * @see java.io.PrintStream#printf(java.util.Locale, java.lang.String, java.lang.Object[])
+	 */
+	@Override
+	public PrintStream printf(Locale l, String format, Object... args) {
+		// See special logic in println. If super.printf(...) gets used, Toolbox
+		// functionality breaks.
+    	throw new UnsupportedOperationException("use println instead");
+	}
+
 	/**
      * Prints a string in to the ToolIO buffer in a separate line
      * @param str String to be printed