Use "set -x" with RUN in Dockerfile

Author: impredicative

Dockerfile

@@ -3,13 +3,15 @@ FROM python:3.8-slim-buster as build
 # As of 2019-11-29, python:3.8-slim-stretch doesn't exist. See https://github.com/docker-library/python/issues/428
 WORKDIR /app
 COPY requirements.txt .
-RUN sed -i 's/@SECLEVEL=2/@SECLEVEL=1/' /etc/ssl/openssl.cnf && \
+RUN set -x && \
+    sed -i 's/@SECLEVEL=2/@SECLEVEL=1/' /etc/ssl/openssl.cnf && \
     pip install --no-cache-dir -U pip wheel && \
     pip install --no-cache-dir -r ./requirements.txt
 # Note: Regarding SECLEVEL, see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=927461
 # Lowering the SECLEVEL causes more https certificates to be valid.
 COPY ircurltitlebot ircurltitlebot
-RUN groupadd -g 999 app && \
+RUN set -x && \
+    groupadd -g 999 app && \
     useradd -r -m -u 999 -g app app
 USER app
 ENTRYPOINT ["python", "-m", "ircurltitlebot"]
@@ -20,7 +22,8 @@ FROM build as test
 WORKDIR /app
 USER root
 COPY Makefile pylintrc pyproject.toml requirements-dev.in setup.cfg vulture.txt ./
-RUN pip install --no-cache-dir -U -r requirements-dev.in && \
+RUN set -x && \
+    pip install --no-cache-dir -U -r requirements-dev.in && \
     apt-get update && apt-get -y install make && \
     make test