docker build fails "Directory examples/dummy_plugin does not exist"

[glennmatthews]

Environment

• Python version: any
• Nautobot version: develop dd731f3

Steps to Reproduce

1. invoke build

Expected Behavior

Successful docker build

Observed Behavior

#13 [dev  7/13] RUN poetry install --no-root --no-ansi
#13 sha256:86597945942e1a01e8da9c3f4e36cca5f68c606e5d57eb19d1c984b844cca421
#13 0.805 
#13 0.805   ValueError
#13 0.805 
#13 0.805   Directory examples/dummy_plugin does not exist
#13 0.805 
#13 0.805   at ~/.poetry/lib/poetry/_vendor/py3.6/poetry/core/packages/directory_dependency.py:41 in __init__
#13 0.818        37│         self._develop = develop
#13 0.818        38│         self._supports_poetry = False
#13 0.819        39│ 
#13 0.819        40│         if not self._full_path.exists():
#13 0.820     →  41│             raise ValueError("Directory {} does not exist".format(self._path))
#13 0.820        42│ 
#13 0.820        43│         if self._full_path.is_file():
#13 0.821        44│             raise ValueError("{} is a file, expected a directory".format(self._path))
#13 0.821        45│ 
#13 ERROR: executor failed running [/bin/sh -c poetry install --no-root --no-ansi]: exit code: 1
------
 > [dev  7/13] RUN poetry install --no-root --no-ansi:
------
executor failed running [/bin/sh -c poetry install --no-root --no-ansi]: exit code: 1
Service 'nautobot' failed to build

[glennmatthews]

Regression introduced by #474.