Fedora 30: ImportError: libnsl.so.1 when importing apache_beam in Python 3

When importing apache_beam in python, it fails because it can't find libnsl.so.1.

It is fixed by running 'dnf install libnsl'.  This appears to be a dependency of Apache Arrow.

output:

Singularity tfx:~/tfx_image_example_gen> python
{{Python 3.6.9 |Anaconda, Inc.| (default, Jul 30 2019, 19:07:31) }}
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import apache_beam
/opt/snps/envs/tfx/lib/python3.6/site-packages/apache_beam/_init_.py:84: UserWarning: Some syntactic constructs of Python 3 are not yet fully supported by Apache Beam.
{{ 'Some syntactic constructs of Python 3 are not yet fully supported by '}}
Traceback (most recent call last):
{{ File "<stdin>", line 1, in <module>}}
{{ File "/opt/snps/envs/tfx/lib/python3.6/site-packages/apache_beam/_init_.py", line 98, in <module>}}
{{ from apache_beam import io}}
{{ File "/opt/snps/envs/tfx/lib/python3.6/site-packages/apache_beam/io/_init_.py", line 29, in <module>}}
{{ from apache_beam.io.parquetio import *}}
{{ File "/opt/snps/envs/tfx/lib/python3.6/site-packages/apache_beam/io/parquetio.py", line 45, in <module>}}
{{ import pyarrow as pa}}
{{ File "/opt/snps/envs/tfx/lib/python3.6/site-packages/pyarrow/_init_.py", line 49, in <module>}}
{{ from pyarrow.lib import cpu_count, set_cpu_count}}
ImportError: libnsl.so.1: cannot open shared object file: No such file or directory