force to use tornado 5.1.1, because tornado 6.0 is creating XSRF token errors

setup.py

@@ -17,7 +17,7 @@ setup(
     description='Extension for Jupyter notebooks to connect to openBIS and download/upload datasets, inluding the notebook itself',
     long_description=long_description,
     long_description_content_type="text/markdown",
-    url='https://sissource.ethz.ch/sispub/jupyter-openbis-integration',
+    url='https://sissource.ethz.ch/sispub/jupyter-openbis-extension',
     packages=find_packages(),
     license='Apache Software License Version 2.0',
     install_requires=[
@@ -25,6 +25,7 @@ setup(
         'jupyter',
         'pybis>=1.8.4',
         'numpy',
+        'tornado==5.1.1',
     ],
     python_requires=">=3.3",
     classifiers=[