robotframework - Error when running Robot Framework with Sikuli

Question

command: C:\Users\han\Desktop\Sikuli-and-Robot-Framework-Integration-master\calctest\robottest.bat robot_suite\verify_operations.txt --argumentfile c:\users\han\appdata\local\temp\RIDE7wtysi.d\argfile.txt --listener C:\Python27\lib\site-packages\robotide\contrib\testrunner\TestRunnerAgent.py:62977:False C:\Users\han\Desktop\Sikuli-and-Robot-Framework-Integration-master\calctest\robot_suite\verify_operations.txt
unexpected error: Exception in thread "main" Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\Users\han\Desktop\Sikuli-and-Robot-Framework-Integration-master\calctest\robotframework-2.5.5.jar\Lib\robot\__init__$py.class", line 16, in <module>
File "C:\Users\han\Desktop\Sikuli-and-Robot-Framework-Integration-master\calctest\sikuli-script.jar\Lib\os.py", line 118, in <module>
ImportError: no os specific module found

Sikuli X - 1.0rc3 (R905) Robot Framework 2.7.7 Python 2.7.5 jython 2.7 b1 Windows 7

robotest.bat

@echo off

set sikuli_jar=C:\Users\han\Desktop\Sikuli-and-Robot-Framework-Integration-master\calctest\sikuli-script.jar

java -cp "robotframework-2.5.5.jar;%sikuli_jar%" ^
 -Dpython.path="%sikuli_jar%/Lib" ^
 org.robotframework.RobotFramework ^
 --pythonpath=CalcLib ^
 --outputdir=results ^
 --loglevel=TRACE ^
 %*

test suite, verify_operations.txt

*** Settings ***
Library           calc.Calculator    WITH NAME    Calculator

*** Test Cases ***
Verify that 2 + 2 = 4
Start App
Verify App
Perform Action    2    +    2
Verify Result    4

Verify that 2 + 2 = 5
Start App
Verify App
Perform Action    2    +    2
Verify Result    5

Click on non-existent button "Exp"
Start App
Verify App
Perform Action    2    exp    2
Verify Result    2

I have Googled the Error and found some answers online. None of them was able to solve my problem.

Thanks in Advance.