Require zstandard version 0.9.0+

In `zstandard`'s `0.9.0` release, support for the Python Buffer Protocol
was added. As we are supporting this functionality with other
compressors, go ahead and support it here too.

Author: jakirkham

continuous_integration/environment-3.10.yaml

@@ -39,7 +39,7 @@ dependencies:
   - toolz
   - tornado
   - zict  # overridden by git tip below
-  - zstandard
+  - zstandard >=0.9.0
   - pip:
       - git+https://github.com/dask/dask
       - git+https://github.com/dask/s3fs

continuous_integration/environment-3.8.yaml

@@ -41,7 +41,7 @@ dependencies:
   - toolz
   - tornado
   - zict
-  - zstandard
+  - zstandard >=0.9.0
   - pip:
       - git+https://github.com/dask/dask
       - git+https://github.com/jcrist/crick  # Only tested here

continuous_integration/environment-3.9.yaml

@@ -44,7 +44,7 @@ dependencies:
   - torchvision  # Only tested here
   - tornado
   - zict
-  - zstandard
+  - zstandard >=0.9.0
   - pip:
       - git+https://github.com/dask/dask
       - keras

distributed/protocol/compression.py

@@ -77,6 +77,10 @@
 with suppress(ImportError):
     import zstandard
 
+    # Required for Python Buffer Protocol support.
+    if parse_version(zstandard.__version__) < parse_version("0.9.0"):
+        raise ImportError("Need zstandard >= 0.9.0")
+
     zstd_compressor = zstandard.ZstdCompressor(
         level=dask.config.get("distributed.comm.zstd.level"),
         threads=dask.config.get("distributed.comm.zstd.threads"),