Fix inability to install new dependencies via the devcontainer

Author: Ben Dickinson

Dockerfile

@@ -3,14 +3,19 @@ FROM python:3.10
 WORKDIR /app
 
 RUN useradd --create-home dpl && \
-    pip install "poetry>=1.1.12,<2" && \
-    poetry config virtualenvs.create false
+    mkdir -p /venv/ && \
+    chown -R dpl:dpl /venv/ /app/
+
+ENV PATH=/venv/bin:/home/dpl/.local/bin:$PATH \
+    VIRTUAL_ENV=/venv/ \
+    DJANGO_SETTINGS_MODULE=tests.settings.dev
+
+USER dpl
+
+RUN pip install --user "poetry>=1.1.12,<2" && \
+    python -m venv /venv/
 
 COPY pyproject.toml ./
 RUN poetry install --no-root
 
-ENV DJANGO_SETTINGS_MODULE=tests.settings.dev \
-    PYTHONPATH=.
-
-USER dpl
 CMD django-admin runserver 0.0.0.0:8000