Deprecate the support for python3.6 (#863)

* prefer install binray for opencv

* clean the code

* rename BinaryPeferredPackageIndex

* adjust minimum version of python

* clean the code

* remove duplicated CI

.circleci/test.yml

@@ -163,7 +163,7 @@ workflows:
           name: minimum_version_cpu
           torch: 1.6.0
           torchvision: 0.7.0
-          python: 3.6.9  # The lowest python 3.6.x version available on CircleCI images
+          python: 3.7.4
           requires:
             - lint
       - build_cpu:

.github/workflows/merge_stage_test.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-18.04
     strategy:
       matrix:
-        python-version: [3.6, 3.8, 3.9]
+        python-version: [3.8, 3.9]
         torch: [1.8.1]
         include:
           - torch: 1.8.1

setup.py

@@ -137,14 +137,13 @@ setup(
         'License :: OSI Approved :: Apache Software License',
         'Operating System :: OS Independent',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         'Topic :: Utilities',
     ],
-    python_requires='>=3.6',
+    python_requires='>=3.7',
     install_requires=install_requires,
     extras_require={
         'all': parse_requirements('requirements.txt'),