fix: use python base image and fix pip version issue (#43)

agent/docker/python/Dockerfile

@@ -4,14 +4,16 @@ ADD . /go/src/github.com/VerizonMedia/kubectl-flame
 RUN go get -d -v ./...
 RUN cd agent && go build -o /go/bin/agent
 
-FROM alpine AS pyspybuild
-RUN apk add python3 py3-pip
-RUN echo 'manylinux1_compatible = True' > /usr/lib/python3.8/site-packages/_manylinux.py
+FROM python:3.8-alpine AS pyspybuild
+# only works with pip version 20.2.4
+# https://github.com/benfred/py-spy/issues/353
+RUN pip install pip==20.2.4
+RUN echo 'manylinux1_compatible = True' > /usr/local/lib/python3.8/site-packages/_manylinux.py
 RUN pip3 install py-spy==0.4.0.dev1
 
-FROM alpine
+FROM python:3.8-alpine
 RUN mkdir /app
 COPY --from=agentbuild /go/bin/agent /app/agent
-COPY --from=pyspybuild /usr/bin/py-spy /app/py-spy
+COPY --from=pyspybuild /usr/local/bin/py-spy /app/py-spy
 
 CMD [ "/app/agent" ]