Remove Pillow<7.0.0 constraint for python 3+

setup.py

@@ -13,16 +13,19 @@
 # * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # * See the License for the specific language governing permissions and
 # * limitations under the License.
+import sys
 
 from setuptools import setup
 from io import open
 
 with open("README.md", "r", encoding="utf8") as fh:
     long_description = fh.read()
 
+pillow_version_constraint = ',<7.0.0' if sys.version_info.major < 3 else ''
+
 setup(
     name='Cytomine-Python-Client',
-    version='2.8.1',
+    version='2.8.2',
     description='Python client to interact with Cytomine.',
     long_description=long_description,
     long_description_content_type="text/markdown",
@@ -44,7 +47,7 @@
                       'six>=1.11.0',
                       'future>=0.17.1',
                       'opencv-python-headless>=3.4.3',
-                      'Pillow>=5.3.0,<7.0.0',
+                      'Pillow>=5.3.0{}'.format(pillow_version_constraint),
                       'requests>=2.22.0',
                       'urllib3>=1.25.2'],
     setup_requires=['pytest-runner'],