[Fix] Adjust the minimum supported python version to 3.7

.circleci/test.yml

@@ -59,7 +59,7 @@ jobs:
             python -m pip install torch==<< parameters.torch >>+cpu torchvision==<< parameters.torchvision >>+cpu -f https://download.pytorch.org/whl/torch_stable.html
       - when:
           condition:
-            equal: [ "3.9.0", << parameters.python >> ]
+            equal: ["3.9.0", << parameters.python >>]
           steps:
             - run: pip install "protobuf <= 3.20.1" && sudo apt-get update && sudo apt-get -y install libprotobuf-dev protobuf-compiler cmake
       - run:
@@ -144,8 +144,7 @@ workflows:
                 - dev-3.x
   pr_stage_test:
     when:
-      not:
-        << pipeline.parameters.lint_only >>
+      not: << pipeline.parameters.lint_only >>
     jobs:
       - lint:
           name: lint
@@ -157,7 +156,7 @@ 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 # The lowest python 3.7.x version available on CircleCI images
           requires:
             - lint
       - build_cpu:
@@ -181,8 +180,7 @@ workflows:
             - hold
   merge_stage_test:
     when:
-      not:
-        << pipeline.parameters.lint_only >>
+      not: << pipeline.parameters.lint_only >>
     jobs:
       - build_cuda:
           name: minimum_version_gpu

docs/en/get_started.md

@@ -4,7 +4,7 @@
 
 In this section, we demonstrate how to prepare an environment with PyTorch.
 
-MMDetection works on Linux, Windows, and macOS. It requires Python 3.6+, CUDA 9.2+, and PyTorch 1.6+.
+MMDetection works on Linux, Windows, and macOS. It requires Python 3.7+, CUDA 9.2+, and PyTorch 1.6+.
 
 ```{note}
 If you are experienced with PyTorch and have already installed it, just skip this part and jump to the [next section](#installation). Otherwise, you can follow these steps for the preparation.

docs/zh_cn/get_started.md

@@ -4,7 +4,7 @@
 
 本节中，我们将演示如何用 PyTorch 准备一个环境。
 
-MMDetection 支持在 Linux，Windows 和 macOS 上运行。它需要 Python 3.6 以上，CUDA 9.2 以上和 PyTorch 1.6 以上。
+MMDetection 支持在 Linux，Windows 和 macOS 上运行。它需要 Python 3.7 以上，CUDA 9.2 以上和 PyTorch 1.6 以上。
 
 ```{note}
 如果你对 PyTorch 有经验并且已经安装了它，你可以直接跳转到[下一小节](#安装流程)。否则，你可以按照下述步骤进行准备。

setup.py

@@ -202,7 +202,6 @@ def add_mim_extension():
             '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',