docker updates

Dockerfile

-FROM python:3.7
+FROM python:3.8
 ENV PYTHONUNBUFFERED 1
 ENV BUILD_PACKAGES pandoc rsync openssh-client build-essential
 
@@ -8,5 +8,5 @@ WORKDIR /code
 RUN apt-get update -y && apt-get install -y $BUILD_PACKAGES
 
 RUN pip install pipenv
-ADD Pipfile Pipfile.lock /code/
-RUN pipenv install --dev --system --deploy
+ADD Pipfile /code/
+RUN pipenv install --dev && pipenv --rm && pipenv install --dev --system --deploy && rm -r /root/.cache/pip*

Pipfile

@@ -15,7 +15,7 @@ mypy = "*"
 pylint = "*"
 sphinx = "*"
 pipenv = "*"
-black = "*"
+black = "==19.3b0"
 pre-commit = "*"
 pydocstyle = "*"
 isort = "*"
@@ -27,7 +27,7 @@ rope = "*"
 pyserial = "*"
 numpy = "*"
 scipy = ">=1.1.0"
-pandas = ">=0.23.3"
+pandas = ">=0.23"
 matplotlib = "*"
 tabulate = "*"
 pytimeparse = "*"
@@ -46,6 +46,3 @@ DateTime = "*"
 pyvisa = "*"
 pyvisa-py = "*"
 docutils = "==0.15.2"
-
-[pipenv]
-allow_prereleases = true