[CT-3396] [Bug] dbt deps --add-package doesn't work when packages.yml contains warn-unpinned: false

[dbeatty10]

Is this a new bug in dbt-core?

• I believe this is a new bug in dbt-core
• I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

As originally reported by @seub in #9076 (comment), the following exception is raised with an accompanying stack trace when packages.yml contains warn-unpinned: false and dbt deps --add-package is executed:

TypeError: argument of type 'bool' is not iterable

Expected Behavior

The --add-package argument should execute without producing an exception and a stack trace.

Steps To Reproduce

packages.yml

packages:
 - git: https://github.com/fivetran/dbt_amplitude
   warn-unpinned: false

Running this will raise the exception:

dbt deps --add-package dbt-labs/dbt_utils@1.0.0

Removing warn-unpinned: false and re-running the command works fine.

Relevant log output

dbt deps --add-package dbt-labs/dbt_utils@1.0.0

03:02:33  Running with dbt=1.7.1
03:02:34  Encountered an error:
argument of type 'bool' is not iterable
03:02:34  Traceback (most recent call last):
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/cli/requires.py", line 90, in wrapper
    result, success = func(*args, **kwargs)
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/cli/requires.py", line 75, in wrapper
    return func(*args, **kwargs)
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/cli/requires.py", line 151, in wrapper
    return func(*args, **kwargs)
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/cli/requires.py", line 197, in wrapper
    return func(*args, **kwargs)
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/cli/main.py", line 492, in deps
    results = task.run()
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/task/deps.py", line 207, in run
    self.add()
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/task/deps.py", line 160, in add
    packages_yml = self.check_for_duplicate_packages(packages_yml)
  File "/path/to/project/.venv/lib/python3.9/site-packages/dbt/task/deps.py", line 138, in check_for_duplicate_packages
    if self.args.add_package["name"] in val:
TypeError: argument of type 'bool' is not iterable

Environment

- OS:
- Python: 3.9.16
- dbt: dbt-core 1.7.1, dbt-snowflake 1.7.0

Which database adapter are you using with dbt?

snowflake

Additional Context

#9076 (comment)

Looking at the code in dbt-core, it seems to me that the in on line 138 should be replaced by an ==.

(Better yet, first find the correct value for val, i.e. the one where the key is package/git/local/tarball. Isn't there a method for that somewhere?)