From e95675de11842205f5a0021092a0a6bbf4a84560 Mon Sep 17 00:00:00 2001
From: Tzu-ping Chung <uranusjr@gmail.com>
Date: Sat, 9 May 2020 05:33:55 +0800
Subject: [PATCH] Allow empty specifier in constraints

---
 src/pip/_internal/resolution/resolvelib/resolver.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/pip/_internal/resolution/resolvelib/resolver.py b/src/pip/_internal/resolution/resolvelib/resolver.py
index 5c94d3dc057..6c85626ebd6 100644
--- a/src/pip/_internal/resolution/resolvelib/resolver.py
+++ b/src/pip/_internal/resolution/resolvelib/resolver.py
@@ -74,8 +74,7 @@ def resolve(self, root_reqs, check_supported_wheels):
         requirements = []
         for req in root_reqs:
             if req.constraint:
-                assert req.name
-                assert req.specifier
+                assert req.name, "constraint should have a name"
                 name = canonicalize_name(req.name)
                 if name in constraints:
                     constraints[name] = constraints[name] & req.specifier