[FLINK-28195][python] Annotate Python3.6 as deprecated in PyFlink 1.16

This closes apache#20078.

flink-python/dev/lint-python.sh

@@ -228,7 +228,7 @@ function install_py_env() {
  if [[ ${BUILD_REASON} = 'IndividualCI' ]]; then
  py_env=("3.9")
  else
- py_env=("3.6" "3.7" "3.8" "3.9")
+ py_env=("3.7" "3.8" "3.9")
  fi
  for ((i=0;i<${#py_env[@]};i++)) do
  if [ -d "$CURRENT_DIR/.conda/envs/${py_env[i]}" ]; then
@@ -403,7 +403,7 @@ function install_environment() {
  fi
 
  # step-3 install python environment which includes
- # 3.6 3.7 3.8 3.9
+ # 3.7 3.8 3.9
  if [ $STEP -lt 3 ] && [ `need_install_component "py_env"` = true ]; then
  print_function "STEP" "installing python environment..."
  install_py_env
@@ -778,7 +778,7 @@ usage: $0 [options]
 -l list all checks supported.
 Examples:
  ./lint-python -s basic => install environment with basic components.
- ./lint-python -s py_env => install environment with python env(3.6,3.7,3.8,3.9).
+ ./lint-python -s py_env => install environment with python env(3.7,3.8,3.9).
  ./lint-python -s all => install environment with all components such as python env,tox,flake8,sphinx,mypy etc.
  ./lint-python -s tox,flake8 => install environment with tox,flake8.
  ./lint-python -s tox -f => reinstall environment with tox.

flink-python/setup.py

@@ -21,6 +21,7 @@
 import os
 import platform
 import sys
+import warnings
 from distutils.command.build_ext import build_ext
 from shutil import copytree, copy, rmtree
 
@@ -30,6 +31,8 @@
  print("Python versions prior to 3.6 are not supported for PyFlink.",
  file=sys.stderr)
  sys.exit(-1)
+elif sys.version_info.minor == 6:
+ warnings.warn("Python version 3.6 won't be supported for PyFlink after 1.16.")
 
 
 def remove_if_exists(file_path):