CSV_EXPORT.encoding config result in gunicorn exception

[georgexsh]

Superset version

Superset 0.26.3
Python 3.5.3 (via docker)

Steps to reproduce

set config:

CSV_EXPORT = {
    'encoding': 'utf-8-sig',
}

click "export csv" of a chart in dashboard page, request /superset/explore_json/?form_data=%7B%22slice_id%22%3A16%7D&csv=true, got an error message:

[ERROR] Error handling request /superset/explore_json/?form_data=%7B%22slice_id%22%3A18%7D&csv
=true
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/gunicorn/workers/sync.py", line 135, in handle
    self.handle_request(listener, req, client, addr)
  File "/usr/local/lib/python3.5/dist-packages/gunicorn/workers/sync.py", line 182, in handle_request
    resp.write(item)
  File "/usr/local/lib/python3.5/dist-packages/gunicorn/http/wsgi.py", line 333, in write
    self.send_headers()
  File "/usr/local/lib/python3.5/dist-packages/gunicorn/http/wsgi.py", line 329, in send_headers
    util.write(self.sock, util.to_bytestring(header_str, "ascii"))
  File "/usr/local/lib/python3.5/dist-packages/gunicorn/util.py", line 507, in to_bytestring
    return value.encode(encoding)
UnicodeEncodeError: 'ascii' codec can't encode characters in position 253-255: ordinal not in range(128)

Root Cause:

dumped headers data result in the exception:

In [7]: dumped.splitlines()
Out[7]:
['HTTP/1.0 200 OK',
...
 'Set-Cookie: session="\\357\\273\\277.eJyNkc1OxSAQRt-FdVOwf9AmxgcxhgwwSCO9VKC3uRrfXXpdmLixy5l853yTzCeRNmJyZLLgE1ZEzoZMBDU3nJtxsGMnmqYb9NiPQgndCeiUaklFdIpW5vCGl5IX0A-NGkXPdCvQ9NhyzsxgkSnomdEWHyyzRhfOBw0eC_PhyrTCK0o3pxzijUzPxOW8ponStK0YE-Z6vuTaQdi3Rdc6LNRABgUJrzPuNLmw0-OYf7EtlT31pYieiSe4onnfMN7uPXfuSVqfJZOH6pGfsvhZ4xIM-l_LGc5AcipANH_Zl4oc7T8_4uTrGwlkmwA.DideRw.-PntEeJCZLJ5k6Y4toho_K6l9ss"; HttpOnly; Path=%EF%BB%BF/?%EF%BB%BF#%EF%BB%BF',
]

notice the strange characters  in the value of Set-Cookie header, they are b'\xef\xbb\xbf' in hex, aka UTF-8 BOM, they are the culprit of this exception.

flask/werkzeug will encode header value with Response.charset, superset has ovrridden charset with the value of CSV_EXPORT.encoding, in PR #3484, but csv encoding is not always http header safe, like utf-8-sig, adds extra BOM bytes that gunicorn dont understand.

related with #5372.

IMHO superset should encode csv data by itself, simplely return encoded binary response, do not rely on Response.charset, which has side effect that will mess up with 8 bits http header value.

--- a/superset/viz.py
+++ b/superset/viz.py
@@ -467,7 +467,9 @@ class BaseViz(object):
     def get_csv(self):
         df = self.get_df()
         include_index = not isinstance(df.index, pd.RangeIndex)
+        r = df.to_csv(index=include_index, **config.get('CSV_EXPORT'))
+        return r.encode(config.get('CSV_EXPORT')['encoding'])

     def get_data(self, df):
         return []

[georgexsh]

with #5377 and #5372, I think superset is still at an early stage in supporting Python3 and non-English language environment, especially on CSV exporting, this feature needs a comprehensive refactor.
as a python3 and Chinese user, I would like to contribute some time to it, but I want to hear thoughts from maintainers and the community first.

[stale]

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[Yiutto]

This is mainly because the cause of the Chinese code, if you are in the download CSV file these mistakes, you can modify the superset of the source code: “site-packages/superset/views/core.py”
f"attachment: filename={query.name}.csv" Modified to attachment: filename=%s.csv" % (quote(query.name))