Pin fastai

Author: rosbo

Dockerfile

@@ -374,7 +374,8 @@ RUN pip install bcolz && \
     pip install widgetsnbextension && \
     pip install pyarrow && \
     pip install feather-format && \
-    pip install fastai && \
+    # b/162850432 unpin once we upgrade to pytorch 1.6
+    pip install fastai~=1.0.61 && \
     pip install allennlp && \
     python -m spacy download en && python -m spacy download en_core_web_lg && \
     apt-get install -y ffmpeg && \