read_csv with Ray engine fails with dialect parameter

[amyskov]

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): Ubuntu 18.04
• Modin version: ce2bea8
• Python version: 3.8.6
• Code we can use to reproduce:

import os

os.environ["MODIN_ENGINE"] = "ray"

import pandas
import modin.pandas as pd
import csv
from modin.pandas.test.utils import df_equals

test_filename = "test.csv"
dialect_name = "test_dialect"


test_csv_dialect_params = {"delimiter": "|"}
csv.register_dialect(dialect_name, **test_csv_dialect_params)
dialect = csv.get_dialect(dialect_name)

kwargs = {
    "filepath_or_buffer": test_filename,
    "dialect": dialect,
}


test_data = """col1,col2,
1,2
3,4
"""

try:
    with open(test_filename, "w") as f:
        f.write(test_data)

    df_pandas = pandas.read_csv(**kwargs)
    print("pandas.read_csv output:\n", df_pandas)
    df_pd = pd.read_csv(**kwargs)
    print("pd.read_csv output:\n", df_pd)
    df_equals(df_pandas, df_pd)
finally:
    os.remove(test_filename)

Describe the problem

Source code / logs

pandas.read_csv output:
   col1,col2,
0        1,2
1        3,4
Traceback (most recent call last):
  File "test.py", line 242, in <module>
    df_pd = pd.read_csv(**kwargs)
  File "/modin/modin/pandas/io.py", line 109, in parser_func
    return _read(**kwargs)
  File "/modin/modin/pandas/io.py", line 127, in _read
    pd_obj = EngineDispatcher.read_csv(**kwargs)
  File "/modin/modin/data_management/factories/dispatcher.py", line 104, in read_csv
    return cls.__engine._read_csv(**kwargs)
  File "/modin/modin/data_management/factories/factories.py", line 87, in _read_csv
    return cls.io_cls.read_csv(**kwargs)
  File "/modin/modin/engines/base/io/file_dispatcher.py", line 29, in read
    query_compiler = cls._read(*args, **kwargs)
  File "/modin/modin/engines/base/io/text/csv_dispatcher.py", line 168, in _read
    partition_id = cls.deploy(cls.parse, num_splits + 2, args)
  File "/modin/modin/engines/ray/task_wrapper.py", line 25, in deploy
    return deploy_ray_func._remote(args=(func, kwargs), num_returns=num_returns)
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/remote_function.py", line 276, in _remote
    return invocation(args, kwargs)
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/remote_function.py", line 262, in invocation
    object_refs = worker.core_worker.submit_task(
  File "python/ray/_raylet.pyx", line 1019, in ray._raylet.CoreWorker.submit_task
  File "python/ray/_raylet.pyx", line 1025, in ray._raylet.CoreWorker.submit_task
  File "python/ray/_raylet.pyx", line 293, in ray._raylet.prepare_args
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/serialization.py", line 404, in serialize
    return self._serialize_to_msgpack(value)
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/serialization.py", line 384, in _serialize_to_msgpack
    self._serialize_to_pickle5(metadata, python_objects)
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/serialization.py", line 344, in _serialize_to_pickle5
    raise e
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/serialization.py", line 340, in _serialize_to_pickle5
    inband = pickle.dumps(
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/cloudpickle/cloudpickle_fast.py", line 70, in dumps
    cp.dump(obj)
  File "/miniconda3/envs/modin_new/lib/python3.8/site-packages/ray/cloudpickle/cloudpickle_fast.py", line 656, in dump
    return Pickler.dump(self, obj)
TypeError: cannot pickle '_csv.Dialect' object

[pyrito]

I am seeing a similar error on the latest master:

TypeError: Could not serialize the argument {'callback': <function CSVDispatcher.read_callback at 0x1bb614310>, 'sep': <no_default>, 'delimiter': None, 'header': 'infer', 'names': <no_default>, 'index_col': None, 'usecols': None, 'prefix': <no_default>, 'mangle_dupe_cols': True, 'dtype': None, 'engine': None, 'converters': None, 'true_values': None, 'false_values': None, 'skipinitialspace': False, 'skiprows': None, 'nrows': None, 'na_values': None, 'keep_default_na': True, 'na_filter': True, 'verbose': False, 'skip_blank_lines': True, 'parse_dates': None, 'infer_datetime_format': False, 'keep_date_col': False, 'date_parser': None, 'dayfirst': False, 'cache_dates': True, 'iterator': False, 'chunksize': None, 'compression': None, 'thousands': None, 'decimal': '.', 'lineterminator': None, 'quotechar': '"', 'quoting': 0, 'escapechar': None, 'comment': None, 'encoding': None, 'encoding_errors': 'strict', 'dialect': <_csv.Dialect object at 0x13497e090>, 'error_bad_lines': None, 'warn_bad_lines': None, 'on_bad_lines': None, 'skipfooter': 0, 'doublequote': True, 'delim_whitespace': False, 'low_memory': True, 'memory_map': False, 'float_precision': None, 'storage_options': None, 'fname': '/Users/kvelayutham/Downloads/data/test.csv', 'num_splits': 1, 'header_size': 1, 'start': 11, 'end': 19} for a task or actor modin.core.execution.ray.common.task_wrapper._deploy_ray_func. Check https://docs.ray.io/en/master/serialization.html#troubleshooting for more information.