[FIX] Revert to pytorch 1.5

- to support CPUs without AVX support

backend/Dockerfile

@@ -13,7 +13,7 @@ RUN curl -SL https://s3.eu-central-1.amazonaws.com/ownphotos-deploy/places365_mo
 RUN curl -SL https://s3.eu-central-1.amazonaws.com/ownphotos-deploy/im2txt_model.tar.gz | tar -zxC /data_models/im2txt/
 RUN curl -SL https://s3.eu-central-1.amazonaws.com/ownphotos-deploy/im2txt_data.tar.gz | tar -zxC /data_models/im2txt/
 RUN curl -SL https://download.pytorch.org/models/resnet152-b121ed2d.pth -o /root/.cache/torch/hub/checkpoints/resnet152-b121ed2d.pth
-RUN pip install torch==1.7.1+cpu torchvision==0.8.2+cpu -f https://download.pytorch.org/whl/torch_stable.html
+RUN pip install torch==1.5.0+cpu torchvision==0.6.0+cpu -f https://download.pytorch.org/whl/torch_stable.html
 RUN pip install -v --install-option="--no" --install-option="DLIB_USE_CUDA" --install-option="--no" --install-option="USE_AVX_INSTRUCTIONS" --install-option="--no" --install-option="USE_SSE4_INSTRUCTIONS" dlib
 # actual project
 ARG DEBUG