From 1988e86b883ace395ba7d18679b5a86f5472b077 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Wed, 11 Apr 2018 08:38:18 -0700
Subject: [PATCH 1/2] fix test failure on Mac

Fixes #4883
---
 mypy/test/testpep561.py | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/mypy/test/testpep561.py b/mypy/test/testpep561.py
index 5d2e3a5963e3..77a5cdf7e906 100644
--- a/mypy/test/testpep561.py
+++ b/mypy/test/testpep561.py
@@ -29,6 +29,18 @@ def check_mypy_run(cmd_line: List[str],
     assert returncode == expected_returncode, returncode
 
 
+def is_in_venv() -> bool:
+    """Returns whether we are running inside a venv.
+
+    Based on https://stackoverflow.com/a/42580137.
+
+    """
+    if hasattr(sys, 'real_prefix'):
+        return True
+    else:
+        return hasattr(sys, 'base_prefix') and sys.base_prefix != sys.prefix
+
+
 class TestPEP561(TestCase):
     @contextmanager
     def install_package(self, pkg: str,
@@ -38,9 +50,7 @@ def install_package(self, pkg: str,
         install_cmd = [python_executable, '-m', 'pip', 'install', '.']
         # if we aren't in a virtualenv, install in the
         # user package directory so we don't need sudo
-        # In a virtualenv, real_prefix is patched onto
-        # sys
-        if not hasattr(sys, 'real_prefix') or python_executable != sys.executable:
+        if not is_in_venv() or python_executable != sys.executable:
             install_cmd.append('--user')
         returncode, lines = run_command(install_cmd, cwd=working_dir)
         if returncode != 0:

From 575767e8892cdcfa38c216963adbf332b6f97d26 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Wed, 11 Apr 2018 09:02:27 -0700
Subject: [PATCH 2/2] add type ignore

---
 mypy/test/testpep561.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mypy/test/testpep561.py b/mypy/test/testpep561.py
index 77a5cdf7e906..7cb65aa487d1 100644
--- a/mypy/test/testpep561.py
+++ b/mypy/test/testpep561.py
@@ -38,7 +38,8 @@ def is_in_venv() -> bool:
     if hasattr(sys, 'real_prefix'):
         return True
     else:
-        return hasattr(sys, 'base_prefix') and sys.base_prefix != sys.prefix
+        # https://github.com/python/typeshed/pull/2047
+        return hasattr(sys, 'base_prefix') and sys.base_prefix != sys.prefix  # type: ignore
 
 
 class TestPEP561(TestCase):