pgAdmin 4 commit: Fixed python exception error when user tries to downl

Fixed python exception error when user tries to download the CSV and there is a connection issue. Fixes #4858

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=c41da41efe88cccd0df9ff75819cd956a70c07b6
Author: Murtuza Zabuawala <murtuza.zabuawala@enterprisedb.com>

Modified Files
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docs/en_US/release_notes_4_21.rst                  |  1 +
.../js/sqleditor/query_tool_http_error_handler.js  |  2 +
web/pgadmin/tools/sqleditor/__init__.py            |  6 +-
web/pgadmin/tools/sqleditor/static/js/sqleditor.js | 64 ++++++++++++++--------
4 files changed, 49 insertions(+), 24 deletions(-)