ElastAlertで使用するPythonを3.6より上にしてDockerコンテナ起動するとJiraのPythonライブラリで「SyntaxError: invalid syntax」が出る

#### エラーメッセージの一部

```
09:49:15.062Z ERROR elastalert-server:
    ProcessController:  Traceback (most recent call last):
      File "/usr/lib/python3.8/runpy.py", line 193, in _run_module_as_main
        return _run_code(code, main_globals, None,
      File "/usr/lib/python3.8/runpy.py", line 86, in _run_code
        exec(code, run_globals)
      File "/opt/elastalert/elastalert/elastalert.py", line 30, in <module>
        from .alerts import DebugAlerter
      File "/opt/elastalert/elastalert/alerts.py", line 26, in <module>
        from jira.client import JIRA
      File "/home/node/.local/lib/python3.8/site-packages/jira/__init__.py", line 10, in <module>
        from jira.client import Comment  # noqa: E402
      File "/home/node/.local/lib/python3.8/site-packages/jira/client.py", line 225
        validate=False, get_server_info=True, async=False, logging=True, max_retries=3, proxies=None,
                                              ^
    SyntaxError: invalid syntax
```

#### 対処方法

[version 0.2.1 broken for python 3.7 (jira) #2437](https://github.com/Yelp/elastalert/issues/2437)

requirements.txtの「jira>=1.0.10,<1.0.15」を「jira>=2.0.0」にしている対応が取りこまれれば問題は解決するが、まだプルリクエストは取り込まれていないので、ElastAlertのDockerイメージ作成時にrequirements.txtでPythonのライブラリを実行する前にrequirements.txtの「jira>=1.0.10,<1.0.15」を「jira>=2.0.0」に書き換えるようにする。ちなみに、setup.pyは「jira>=2.0.0」になっていた。

[ServerCentral/elastalert-server](https://github.com/ServerCentral/elastalert-server) のDockerfileを変更

```:Dockerfile
FROM python:3.8.2-alpine3.11 as py-ea
ARG ELASTALERT_VERSION=v0.2.4
ENV ELASTALERT_VERSION=${ELASTALERT_VERSION}
ARG ELASTALERT_URL=https://github.com/Yelp/elastalert/archive/$ELASTALERT_VERSION.zip
ENV ELASTALERT_URL=${ELASTALERT_URL}
ENV ELASTALERT_HOME /opt/elastalert

WORKDIR /opt

RUN apk add --update --no-cache ca-certificates openssl-dev openssl python3-dev python3 libffi-dev gcc musl-dev wget && \
    wget -O elastalert.zip "${ELASTALERT_URL}" && \
    unzip elastalert.zip && \
    rm elastalert.zip && \
    mv e* "${ELASTALERT_HOME}"

WORKDIR "${ELASTALERT_HOME}"

RUN python3 setup.py install

FROM node:alpine
LABEL maintainer="John Susek <john@johnsolo.net>"
ENV TZ Etc/UTC

RUN apk add --update --no-cache curl tzdata python3 ca-certificates openssl-dev openssl python3-dev gcc musl-dev make libffi-dev libmagic wget

COPY --from=py-ea /usr/lib/python3.8/site-packages /usr/lib/python3.8/site-packages
COPY --from=py-ea /opt/elastalert /opt/elastalert
# COPY --from=py-ea /usr/bin/elastalert* /usr/bin/

WORKDIR /opt/elastalert-server
COPY . /opt/elastalert-server

RUN npm install --production --quiet
COPY config/elastalert.yaml /opt/elastalert/config.yaml
COPY config/config.json config/config.json
COPY rule_templates/ /opt/elastalert/rule_templates
COPY elastalert_modules/ /opt/elastalert/elastalert_modules

# Add default rules directory
# Set permission as unpriviledged user (1000:1000), compatible with Kubernetes
RUN mkdir -p /opt/elastalert/rules/ /opt/elastalert/server_data/tests/ \
    && chown -R node:node /opt

USER node

EXPOSE 3030

WORKDIR /opt/elastalert

# version 0.2.1 broken for python 3.7 (jira) #2437 (https://github.com/Yelp/elastalert/issues/2437)
RUN sed -i 's/jira>=1.0.10,<1.0.15/jira>=2.0.0/g' requirements.txt && \
    pip3 install -r requirements.txt --user

WORKDIR /opt/elastalert-server

ENTRYPOINT ["npm", "start"]
```

#### ServerCentral/elastalert-serverのGitHubのサイトでプルリクエスト

[Update dockerfile for python3.8 and elastalert 0.2.4 #4](https://github.com/ServerCentral/elastalert-server/pull/4)