pgAdmin 4 commit: Added Python 3.8 support. Fixes #5179

Added Python 3.8 support. Fixes #5179
1) Upgraded passlib==1.7.1 to passlib==1.7.2
2) Replace unmaintained Flask-Security with maintained Flask-Security-Too package, which is also compatible with python 3.8
3) Other compatibility code changes.

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=915b09255c9d1aba560a6e79841459663c399509
Author: Aditya Toshniwal <aditya(dot)toshniwal(at)enterprisedb(dot)com>

Modified Files
--------------
docs/en_US/release_notes_4_19.rst | 1 +
requirements.txt | 4 +-
web/pgadmin/browser/__init__.py | 4 +-
.../servers/databases/schemas/utils.py | 2 +-
.../pg_utilities_backup_restore_test.py | 4 +-
.../tools/backup/tests/test_backup_message.py | 16 +--
.../tools/backup/tests/test_batch_process.py | 115 +++++++++++----------
.../tests/test_batch_process_maintenance.py | 99 +++++++++---------
.../maintenance/tests/test_maintenance_message.py | 24 ++---
.../tools/restore/tests/test_batch_process.py | 105 +++++++++----------
.../tools/restore/tests/test_restore_message.py | 8 +-
web/pgadmin/utils/driver/psycopg2/connection.py | 6 +-
web/pgadmin/utils/html.py | 8 +-
13 files changed, 203 insertions(+), 193 deletions(-)