drop support for Python 3.4

https://devguide.python.org/devcycle/#end-of-life-branches

dockerfiles/buildwheel.sh

@@ -4,7 +4,7 @@ set -e -x
 ARCH=`uname -p`
 echo "arch=$ARCH"
 
-for V in cp38-cp38m cp37-cp37m cp36-cp36m cp35-cp35m cp34-cp34m cp27-cp27m cp27-cp27mu; do
+for V in cp38-cp38m cp37-cp37m cp36-cp36m cp35-cp35m cp27-cp27m cp27-cp27mu; do
     PYBIN=/opt/python/$V/bin
     rm -rf build src/cchardet/__pycache__ src/cchardet/*.cpp src/cchardet/*.pyc src/cchardet/*.so src/cchardet.egg-info src/tests/__pycache__ src/tests/*.pyc
     $PYBIN/pip install -r requirements-dev.txt

dockerfiles/develop/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.4-wheezy
+FROM python:3.8-buster
 
 RUN pip install -U cython chardet nose
 

dockerfiles/slim/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.4-slim
+FROM python:3.8-slim-buster
 
 ENV BUILD_DEPS gcc g++