Several IO tests fail in Python 3 with RuntimeError('dictionary changed size during iteration',)}

ERROR: test_delete_dir (apache_beam.io.hadoopfilesystem_test.HadoopFileSystemTest)
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Traceback (most recent call last):
File "/usr/local/google/home/valentyn/projects/beam/clean_head/beam/sdks/python/apache_beam/io/hadoopfilesystem_test.py", line 506, in test_delete_dir
self.fs.delete([url_t1])
File "/usr/local/google/home/valentyn/projects/beam/clean_head/beam/sdks/python/apache_beam/io/hadoopfilesystem.py", line 370, in delete
raise BeamIOError("Delete operation failed", exceptions)
apache_beam.io.filesystem.BeamIOError: Delete operation failed with exceptions

{'hdfs://test_dir/new_dir1': RuntimeError('dictionary changed size during iteration', )}