updated readme

README.md

@@ -108,7 +108,13 @@ HDF5_VERSION=X.Y.Z pip install --no-binary=h5py h5py --no-cache-dir --ignore-ins
 with `X`, `Y`, `Z` replaced by the version needed.  To find the version ScannerBit uses, run (while NOT in the pyscannerbit directory):
 
 ```
-python3 -c "from pyscannerbit import ext_module as ext; print(ext.sb.get_hdf5_version())" 
+python -c "from pyscannerbit import ext_module as ext; print(\"hdf5 version:\", ext.sb.get_hdf5_version())" 
+```
+
+Also, on macs, especially if you're on a shared network drive, you may need to set:
+
+```
+export HDF5_USE_FILE_LOCKING=FALSE
 ```
 
 License