Use Ubuntu focal

Dockerfile

@@ -1,13 +1,13 @@
-FROM ubuntu:cosmic as base-dist
+FROM ubuntu:focal as base-dist
 
 ENV DEBIAN_FRONTEND=noninteractive
 RUN \
   apt-get update && \
   apt-get install --assume-yes --no-install-recommends \
-      python3 graphicsmagick pdftk-java vim \
-      tesseract-ocr tesseract-ocr-fra tesseract-ocr-deu tesseract-ocr-eng \
-      libimage-exiftool-perl software-properties-common \
-      python3-pip python3-setuptools && \
+  python3 graphicsmagick pdftk-java vim \
+  tesseract-ocr tesseract-ocr-fra tesseract-ocr-deu tesseract-ocr-eng \
+  libimage-exiftool-perl software-properties-common \
+  python3-pip python3-setuptools && \
   python3 -m pip install PyYaml numpy scipy scikit-image opencv-python-headless deskew && \
   apt-get auto-remove --assume-yes python3-pip python3-setuptools && \
   apt-get clean && \
@@ -16,7 +16,7 @@ RUN \
 CMD ["/opt/process"]
 
 VOLUME /source \
-    /destination
+  /destination
 
 ENV LANG=C.UTF-8
 
@@ -27,7 +27,7 @@ RUN \
   . /etc/os-release && \
   apt-get update
 RUN DEBIAN_FRONTEND=noninteractive apt-get install --assume-yes --no-install-recommends \
-    python3-wheel python3-pip python3-setuptools poppler-utils ghostscript graphviz
+  python3-wheel python3-pip python3-setuptools poppler-utils ghostscript graphviz
 RUN python3 -m pip install 'pytest<4.0.0' pylint pyflakes bandit mypy codespell coverage pytest-profiling
 
 WORKDIR /opt
@@ -51,6 +51,6 @@ RUN \
   . /etc/os-release && \
   apt-get update && \
   DEBIAN_FRONTEND=noninteractive apt-get install --assume-yes --no-install-recommends \
-      tesseract-ocr-all && \
+  tesseract-ocr-all && \
   apt-get clean && \
   rm --recursive --force /var/lib/apt/lists/* /var/cache/*