Update unsafe packages set to use internal constant

One less thing that ties us to poetry proper

tox_poetry_installer/_poetry.py

@@ -32,7 +32,6 @@ try:
     from poetry.installation.pip_installer import PipInstaller
     from poetry.io.null_io import NullIO
     from poetry.poetry import Poetry
-    from poetry.puzzle.provider import Provider
     from poetry.utils.env import VirtualEnv
 except ImportError:
     raise exceptions.PoetryNotInstalledError(

tox_poetry_installer/constants.py

@@ -5,6 +5,7 @@ in this module.
 
 All constants should be type hinted.
 """
+from typing import Set
 from typing import Tuple
 
 from tox_poetry_installer import __about__
@@ -17,3 +18,6 @@ PEP508_VERSION_DELIMITERS: Tuple[str, ...] = ("~=", "==", "!=", ">", "<")
 # Prefix all reporter messages should include to indicate that they came from this module in the
 # console output.
 REPORTER_PREFIX: str = f"{__about__.__title__}:"
+
+# Internal list of packages that poetry has deemed unsafe and are excluded from the lockfile
+UNSAFE_PACKAGES: Set[str] = {"distribute", "pip", "setuptools", "wheel"}

tox_poetry_installer/utilities.py

@@ -89,8 +89,6 @@ def identify_transients(
     .. note:: The package corresponding to the dependency specified by the ``dep`` parameter will
               be included in the returned list of packages.
     """
-    from tox_poetry_installer import _poetry
-
     transients: List[PoetryPackage] = []
     searched: Set[str] = set()
 
@@ -114,7 +112,7 @@ def identify_transients(
     except KeyError as err:
         dep_name = err.args[0]
 
-        if dep_name in _poetry.Provider.UNSAFE_PACKAGES:
+        if dep_name in constants.UNSAFE_PACKAGES:
             logger.warning(
                 f"Installing package '{dep_name}' using Poetry is not supported and will be skipped"
             )