Bump minimum python version to 3.5.3 (#715)

Author: Strilanc

python2.7-generate.sh

@@ -86,8 +86,8 @@ cp "${in_dir}/LICENSE" "${out_dir}/LICENSE"
 cp "${in_dir}/setup.py" "${out_dir}/setup.py"
 
 # Substitute versions (failing via grep triggering -e if not present.)
-grep "python_requires='>=3.5'" "${out_dir}/setup.py" > /dev/null
-sed -i "s/python_requires='>=3.5'/python_requires='==2.7.*'/" "${out_dir}/setup.py"
+grep "python_requires='>=3.5.3'" "${out_dir}/setup.py" > /dev/null
+sed -i "s/python_requires='>=3.5.3'/python_requires='==2.7.*'/" "${out_dir}/setup.py"
 
 # Mark every file as using utf8 encoding.
 files_to_update=$(find ${out_dir} | grep "\.py$" | grep -v "_pb2\.py$")

setup.py

@@ -44,7 +44,7 @@
     url='http://github.com/quantumlib/cirq',
     author='The Cirq Developers',
     author_email='[email protected]',
-    python_requires='>=3.5',
+    python_requires='>=3.5.3',
     install_requires=requirements,
     license='Apache 2',
     description=description,