#nosec not working for multi-line strings in python 3.8

The Problem

Starting python3.8 adding #nosec after a multi-line string has no effect. This was not the case in python 3.6 (and I think also 3.7)

How to Reproduce

Prepare two sample python source files

success.py:

table = "my_table"
query = f"SELECT * FROM {table}"  # nosec

fail.py

table = "my_table"
query = f"""
SELECT *
FROM {table}
"""  # nosec

Set up python3.6 and python3.8 environments

$ python3.6 -m venv venv36
$ python3.8 -m venv venv38

Run bandit using python3.6

$ source ./venv36/bin/activate
$ pip install bandit==1.6.3

Run bandit on success.py -- no issues.

$ bandit success.py
[main]  INFO    profile include tests: None
[main]  INFO    profile exclude tests: None
[main]  INFO    cli include tests: None
[main]  INFO    cli exclude tests: None
[main]  INFO    running on Python 3.6.12
[node_visitor]  INFO    Unable to find qualified name for module: success.py
Run started:2020-12-07 14:35:50.699373

Test results:
        No issues identified.

Code scanned:
        Total lines of code: 2
        Total lines skipped (#nosec): 1

Run metrics:
        Total issues (by severity):
                Undefined: 0.0
                Low: 0.0
                Medium: 0.0
                High: 0.0
        Total issues (by confidence):
                Undefined: 0.0
                Low: 0.0
                Medium: 0.0
                High: 0.0
Files skipped (0):

Run bandit on fail.py -- no issues either.

$ bandit fail.py
[main]  INFO    profile include tests: None
[main]  INFO    profile exclude tests: None
[main]  INFO    cli include tests: None
[main]  INFO    cli exclude tests: None
[main]  INFO    running on Python 3.6.12
[node_visitor]  INFO    Unable to find qualified name for module: fail.py
Run started:2020-12-07 14:25:36.277457

Test results:
        No issues identified.

Code scanned:
        Total lines of code: 5
        Total lines skipped (#nosec): 1

Run metrics:
        Total issues (by severity):
                Undefined: 0.0
                Low: 0.0
                Medium: 0.0
                High: 0.0
        Total issues (by confidence):
                Undefined: 0.0
                Low: 0.0
                Medium: 0.0
                High: 0.0
Files skipped (0):
$ deactivate

Run bandit in python3.8

$ source ./venv38/bin/activate
$ pip install bandit==1.6.3

Run bandit on success.py -- no issues.

$ bandit success.py 
[main]  INFO    profile include tests: None
[main]  INFO    profile exclude tests: None
[main]  INFO    cli include tests: None
[main]  INFO    cli exclude tests: None
[main]  INFO    running on Python 3.8.6
[node_visitor]  INFO    Unable to find qualified name for module: success.py
Run started:2020-12-07 14:37:02.909155

Test results:
        No issues identified.

Code scanned:
        Total lines of code: 2
        Total lines skipped (#nosec): 1

Run metrics:
        Total issues (by severity):
                Undefined: 0.0
                Low: 0.0
                Medium: 0.0
                High: 0.0
        Total issues (by confidence):
                Undefined: 0.0
                Low: 0.0
                Medium: 0.0
                High: 0.0
Files skipped (0):

Run bandit on fail.py -- one issue is reported.

$ bandit fail.py           
[main]  INFO    profile include tests: None
[main]  INFO    profile exclude tests: None
[main]  INFO    cli include tests: None
[main]  INFO    cli exclude tests: None
[main]  INFO    running on Python 3.8.6
[node_visitor]  INFO    Unable to find qualified name for module: fail.py
Run started:2020-12-07 14:26:41.664117

Test results:
>> Issue: [B608:hardcoded_sql_expressions] Possible SQL injection vector through string-based query construction.
   Severity: Medium   Confidence: Low
   Location: fail.py:2
   More Info: https://bandit.readthedocs.io/en/latest/plugins/b608_hardcoded_sql_expressions.html
1       table = "my_table"
2       query = f"""
3       SELECT *
4       FROM {table}
5       """  # nosec

--------------------------------------------------

Code scanned:
        Total lines of code: 5
        Total lines skipped (#nosec): 0

Run metrics:
        Total issues (by severity):
                Undefined: 0.0
                Low: 0.0
                Medium: 1.0
                High: 0.0
        Total issues (by confidence):
                Undefined: 0.0
                Low: 1.0
                Medium: 0.0
                High: 0.0
Files skipped (0):
$ deactivate

Expected Behaviour

The #nosec clause should work both in python3.6 and python3.8. In this concrete example bandit fail.py should not fail in python3.8.

Bandit Version

On python3.6:

$ bandit --version
bandit 1.6.3
  python version = 3.6.12 (default, Nov  6 2020, 13:08:49) [GCC Apple LLVM 12.0.0 (clang-1200.0.32.21)]

On python3.8

$ bandit --version
bandit 1.6.3
  python version = 3.8.6 (default, Nov  6 2020, 13:26:24) [Clang 12.0.0 (clang-1200.0.32.21)]

Start with the supplied success.py and fail.py examples and reproduce the difference under Python 3.6 and 3.8 using bandit 1.6.3. Trace how Bandit handles the trailing #nosec comment for a multi-line f-string, then add coverage for the failing case and confirm that bandit fail.py reports no issue when the expected suppression is restored.