Declare pep517 dependency (#1353)

piptools/scripts/compile.py

@@ -6,10 +6,10 @@
 
 import click
 from click.utils import LazyFile, safecall
+from pep517 import meta
 from pip._internal.commands import create_command
 from pip._internal.req.constructors import install_req_from_line
 from pip._internal.utils.misc import redact_auth_from_url
-from pip._vendor.pep517 import meta
 
 from .._compat import parse_requirements
 from ..cache import DependencyCache

setup.cfg

@@ -30,6 +30,7 @@ packages = find:
 zip_safe = false
 install_requires =
     click >= 7
+    pep517
     pip >= 20.3
 
 [options.packages.find]