add StringUtil.isOnlyDigits and CommandShellException.getMessage

src/main/java/org/cobbzilla/util/string/StringUtil.java

@@ -109,6 +109,7 @@ public class StringUtil {
     public static String safeShellUrlArg (String s) { return s.replaceAll("[^-\\.&?:@+_%/=\\w]+", ""); }
 
     public static String onlyDigits (String s) { return s.replaceAll("\\D+", ""); }
+    public static boolean isOnlyDigits (String s) { return onlyDigits(s).equals(s); }
 
     public static String removeWhitespace (String s) { return s.replaceAll("\\p{javaSpaceChar}", ""); }
 

src/main/java/org/cobbzilla/util/system/CommandShellException.java

@@ -11,6 +11,8 @@ public class CommandShellException extends RuntimeException {
     @Getter @Setter private CommandResult result;
     @Getter @Setter private Exception exception;
 
+    @Override public String getMessage() { return toString(); }
+
     public CommandShellException (CommandResult result) { this.result = result; }
 
     public CommandShellException (Exception e) { this.exception = e; }