From dcaf7ecc5225cc63d9235b284f6c90fc3ce43eeb Mon Sep 17 00:00:00 2001
From: Frost Ming <mianghong@gmail.com>
Date: Sat, 15 Jun 2019 18:20:12 +0800
Subject: [PATCH] do not combine lists

---
 pipenv/core.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pipenv/core.py b/pipenv/core.py
index 7fa8a3f1..32f5e2fa 100644
--- a/pipenv/core.py
+++ b/pipenv/core.py
@@ -664,7 +664,7 @@ def _cleanup_procs(procs, failed_deps_queue, retry=True):
                 # We echo both c.out and c.err because pip returns error details on out.
                 err = c.err.strip().splitlines() if c.err else []
                 out = c.out.strip().splitlines() if c.out else []
-                err_lines = [line for line in (out + err)]
+                err_lines = [line for message in [out, err] for line in message]
                 # Return the subprocess' return code.
                 raise exceptions.InstallError(c.dep.name, extra=err_lines)
             # Save the Failed Dependency for later.