Ensure candidate name is canonicalised

src/pip/_internal/resolution/resolvelib/candidates.py

+from pip._vendor.packaging.utils import canonicalize_name
+
 from pip._internal.req.constructors import install_req_from_line
 from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -76,7 +78,7 @@ class LinkCandidate(Candidate):
     def name(self):
         # type: () -> str
         if self._name is None:
-            self._name = self.dist.project_name
+            self._name = canonicalize_name(self.dist.project_name)
         return self._name
 
     @property

src/pip/_internal/resolution/resolvelib/requirements.py

@@ -103,6 +103,8 @@ class SpecifierRequirement(Requirement):
 
     def is_satisfied_by(self, candidate):
         # type: (Candidate) -> bool
+
         assert candidate.name == self.name, \
-            "Internal issue: Candidate is not for this requirement"
+            "Internal issue: Candidate is not for this requirement " \
+            " {} vs {}".format(candidate.name, self.name)
         return candidate.version in self._ireq.req.specifier