fix: force python 2.7 dependency

Dockerfile

@@ -8,7 +8,7 @@ RUN curl --silent --location https://rpm.nodesource.com/setup_8.x | bash -; yum
 RUN npm install -g --save-dev @commitlint/{cli,config-conventional}; npm install -g conventional-changelog-cli
 RUN echo "module.exports = {extends: ['@commitlint/config-conventional']};" > commitlint.config.js
 
-RUN pip install --upgrade pip setuptools future; pip install coverage; pip install pytest; pip install pytest-cov
+RUN pip install --upgrade pip setuptools; pip install coverage; pip install pytest; pip install pytest-cov
 
 RUN wget http://www2.ccpn.ac.uk/download/ccpnmr/analysis2.4.2.tar.gz; tar xvzf analysis2.4.2.tar.gz; export CCPNMR_TOP_DIR=$(pwd)/ccpnmr; export PYTHONPATH=${PYTHONPATH}:$CCPNMR_TOP_DIR/ccpnmr2.4/python
 
@@ -18,5 +18,5 @@ ADD *.py PKG-INFO /build-aria/
 RUN ls build-aria/src/aria
 RUN type pip; type python
 RUN pip --version
-RUN cd build-aria; pip install .; npm install --save-dev husky
+RUN cd build-aria; /usr/lib/python2.7/site-packages/pip install .; npm install --save-dev husky
 RUN npx yarn add husky --dev

setup.py

@@ -203,6 +203,7 @@ def setup_package():
         },
         classifiers=[_f for _f in CLASSIFIERS.split('\n') if _f],
         platforms=["Linux", "Solaris", "Mac OS-X", "Unix"],
+        python_requires='>=2.7,<3.0.*',
         setup_requires=[
             # Setuptools 18.0 properly handles Cython extensions.
             'setuptools>=18.0',