Read file lines as text in python2 as well (#1237)

Author: asottile

docs/changelog/1234.bugfix.rst

@@ -0,0 +1 @@
+Fix sdist creation on python2.x when there is non-ascii output.

src/tox/action.py

@@ -104,7 +104,7 @@ def popen(
                 exit_code = process.returncode
             finally:
                 if out_path is not None and out_path.exists():
-                    lines = out_path.read().split("\n")
+                    lines = out_path.read_text("UTF-8").split("\n")
                     # first three lines are the action, cwd, and cmd - remove it
                     output = "\n".join(lines[3:])
                 try:

tests/unit/test_z_cmdline.py

@@ -805,6 +805,25 @@ def test_env_VIRTUALENV_PYTHON(initproj, cmd, monkeypatch):
     assert "create" in result.out
 
 
+def test_setup_prints_non_ascii(initproj, cmd):
+    initproj(
+        "example123",
+        filedefs={
+            "setup.py": """\
+import sys
+getattr(sys.stdout, 'buffer', sys.stdout).write(b'\\xe2\\x98\\x83\\n')
+
+import setuptools
+setuptools.setup(name='example123')
+""",
+            "tox.ini": "",
+        },
+    )
+    result = cmd("--notest")
+    result.assert_success()
+    assert "create" in result.out
+
+
 def test_envsitepackagesdir(cmd, initproj):
     initproj(
         "pkg512-0.0.5",