Fix default language change in constants file from docker build.

docker/Dockerfile

@@ -39,7 +39,7 @@ RUN mkdir -p "${BOT_HOME_DIR}" && \
     pip3 install Pillow==6.0.0 && \
     cd TLG_JoinCaptchaBot/sources && \
     sed -i -e "s/${INVALID_TOKEN}/${BOT_TOKEN}/g" constants.py && \
-    sed -i -e "s/^\(\s\+'INIT_LANG'\)[^:]*:.*/\1 : '${BOT_LANG}',/g" constants.py && \
+    sed -i -e "s/^\(\s\+\"INIT_LANG\"\)[^:]*:.*/\1 : \"${BOT_LANG}\",/g" constants.py && \
     chown -R "${BOT_USER}":"${BOT_USER}" "${BOT_HOME_DIR}" && \
     echo "rm -f ./data/captchas/*; python3 -u join_captcha_bot.py" >run_in_docker && \
     chmod 755 kill run run_in_docker status && \

docker/README.md

@@ -32,7 +32,7 @@ It is also possible to specify a different default language for the bot to use
 by setting the `BOT_LANG` variable at build time, like:
 
 ```
-make BOT_TOKEN="<your_bot_token_here> BOT_LANG="PT_BR"
+make BOT_TOKEN="<your_bot_token_here>" BOT_LANG="PT_BR"
 ```
 
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