From 69e88293bbc0c9915ded9eb0c2200455fb062d91 Mon Sep 17 00:00:00 2001
From: Albert Tugushev <albert@tugushev.ru>
Date: Wed, 24 Apr 2019 12:10:03 +0700
Subject: [PATCH] Fix pip>=19.1 compatibility

---
 piptools/repositories/pypi.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/piptools/repositories/pypi.py b/piptools/repositories/pypi.py
index 08449d808..0f218443c 100644
--- a/piptools/repositories/pypi.py
+++ b/piptools/repositories/pypi.py
@@ -144,7 +144,16 @@ def find_best_match(self, ireq, prereleases=None):
         matching_candidates = [candidates_by_version[ver] for ver in matching_versions]
         if not matching_candidates:
             raise NoCandidateFound(ireq, all_candidates, self.finder)
-        best_candidate = max(matching_candidates, key=self.finder._candidate_sort_key)
+
+        # pip <= 19.0.3
+        if hasattr(self.finder, "_candidate_sort_key"):
+            best_candidate = max(
+                matching_candidates, key=self.finder._candidate_sort_key
+            )
+        # pip >= 19.1
+        else:
+            evaluator = self.finder.candidate_evaluator
+            best_candidate = evaluator.get_best_candidate(matching_candidates)
 
         # Turn the candidate into a pinned InstallRequirement
         return make_install_requirement(