v0.16.1: dbt deps doesn't respect "--project-dir" flag

[nickwu241]

I've attempted to fix the bug at #2339

Describe the bug

Upgrading from version v0.16.0 to v0.16.1 breaks running dbt deps --project-dir project when the dbt deps --project-dir command is run from outside the project directory.

--project-dir flag is not respected anymore.

Steps To Reproduce

On v0.16.1 this will fail

1. cd .. from a dbt project directory

2. dbt deps --project-dir project will fail

Example directory structure: https://github.com/nickwu241/dbt-bug
Example Logs of working in v0.16.0 but not v0.16.1:

~/dbt-bug/project                                                                                 env
❯ cd ..
~/dbt-bug                                                                                         env
❯ dbt deps --project-dir project
Running with dbt=0.16.0
Installing https://github.com/fishtown-analytics/dbt-utils.git@0.1.21
  Installed from revision 0.1.21

~/dbt-bug                                                                                     5s  env
❯ dbt deps --project-dir project
Running with dbt=0.16.1
Encountered an error while reading the project:
  ERROR: Runtime Error
  no dbt_project.yml found at expected path /Users/nickwu/dbt-bug/dbt_project.yml
Encountered an error:
Runtime Error
  Could not run dbt

With --debug:

❯ dbt --debug deps --project-dir project
2020-04-17 09:16:55.283620 (MainThread): Running with dbt=0.16.1
2020-04-17 09:16:55.283825 (MainThread): Encountered an error while reading the project:
2020-04-17 09:16:55.283966 (MainThread):   ERROR: Runtime Error
  no dbt_project.yml found at expected path /Users/nickwu/dbt-bug/dbt_project.yml
2020-04-17 09:16:55.289265 (MainThread): Sending event: {'category': 'dbt', 'action': 'invocation', 'label': 'invalid', 'context': [<snowplow_tracker.self_describing_json.SelfDescribingJson object at 0x10b4248d0>, <snowplow_tracker.self_describing_json.SelfDescribingJson object at 0x10b440690>, <snowplow_tracker.self_describing_json.SelfDescribingJson object at 0x10b440cd0>]}
2020-04-17 09:16:55.289927 (MainThread): Encountered an error:
2020-04-17 09:16:55.290013 (MainThread): Runtime Error
  Could not run dbt
2020-04-17 09:16:55.290995 (MainThread): Traceback (most recent call last):
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/task/base.py", line 59, in from_args
    config = cls.ConfigType.from_args(args)
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/config/runtime.py", line 310, in from_args
    partial = Project.partial_load(os.getcwd())
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/config/project.py", line 508, in partial_load
    project_dict = _raw_project_from(project_root)
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/config/project.py", line 193, in _raw_project_from
    .format(project_yaml_filepath)
dbt.exceptions.DbtProjectError: Runtime Error
  no dbt_project.yml found at expected path /Users/nickwu/dbt-bug/dbt_project.yml

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/main.py", line 81, in main
    results, succeeded = handle_and_check(args)
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/main.py", line 159, in handle_and_check
    task, res = run_from_args(parsed)
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/main.py", line 198, in run_from_args
    task = parsed.cls.from_args(args=parsed)
  File "/Users/nickwu/src/github.com/nickwu241/dbt/core/dbt/task/base.py", line 67, in from_args
    raise dbt.exceptions.RuntimeException('Could not run dbt') from exc
dbt.exceptions.RuntimeException: Runtime Error
  Could not run dbt

Expected behavior

dbt deps --project-dir project should install packages for my dbt project at project directory.

Screenshots and log output

Please see Steps to Reproduce.

System information

Which database are you using dbt with?

• postgres
• redshift
• bigquery
• snowflake
• other (specify: ____________)

The output of dbt --version:

installed version: 0.16.1
   latest version: 0.16.1

Up to date!

The operating system you're using: macOS

The output of python --version: Python 3.7.5