Use \n instead if \r\n as line separator (#1905)

The logging framework will write to a pipe, which then will blindly transform
all carriage returns to carriage return plus line feed, when on Windows. So
injecting the \r\n leaves us with double carriage return.

Signed-off-by: Bernat Gabor <bgabor8@bloomberg.net>

docs/changelog/1905.bugfix.rst

@@ -0,0 +1,2 @@
+Use ``\n`` instead if ``\r\n`` as line separator for report (because Python already performs this transformation
+automatically upon write to the logging pipe) - by :user:`gaborbernat`.

src/virtualenv/__main__.py

@@ -1,7 +1,6 @@
 from __future__ import absolute_import, print_function, unicode_literals
 
 import logging
-import os
 import sys
 from datetime import datetime
 
@@ -52,7 +51,7 @@ def __str__(self):
             )
         if self.session.activators:
             lines.append("  activators {}".format(",".join(i.__class__.__name__ for i in self.session.activators)))
-        return os.linesep.join(lines)
+        return "\n".join(lines)
 
 
 def run_with_catch(args=None):

src/virtualenv/config/ini.py

@@ -75,7 +75,7 @@ def __bool__(self):
     def epilog(self):
         msg = "{}config file {} {} (change{} via env var {})"
         return msg.format(
-            os.linesep,
+            "\n",
             self.config_file,
             self.STATE[self.has_config_file],
             "d" if self.is_env_var else "",

tests/unit/config/test___main__.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import, unicode_literals
 
+import os
 import re
 import sys
 
@@ -65,8 +66,13 @@ def test_session_report_full(session_app_data, tmp_path, capsys):
         r"    added seed packages: .*pip==.*, setuptools==.*, wheel==.*",
         r"  activators .*",
     ]
+    _match_regexes(lines, regexes)
+
+
+def _match_regexes(lines, regexes):
     for line, regex in zip(lines, regexes):
-        assert re.match(regex, line), line
+        comp_regex = re.compile(r"^{}$".format(regex))
+        assert comp_regex.match(line), line
 
 
 def test_session_report_minimal(session_app_data, tmp_path, capsys):
@@ -78,5 +84,18 @@ def test_session_report_minimal(session_app_data, tmp_path, capsys):
         r"created virtual environment .* in \d+ms",
         r"  creator .*",
     ]
-    for line, regex in zip(lines, regexes):
-        assert re.match(regex, line), line
+    _match_regexes(lines, regexes)
+
+
+def test_session_report_subprocess(session_app_data, tmp_path):
+    # when called via a subprocess the logging framework should flush and POSIX line normalization happen
+    out = subprocess.check_output(
+        [sys.executable, "-m", "virtualenv", str(tmp_path), "--activators", "powershell", "--without-pip"],
+    )
+    lines = out.decode().split(os.linesep)
+    regexes = [
+        r"created virtual environment .* in \d+ms",
+        r"  creator .*",
+        r"  activators .*",
+    ]
+    _match_regexes(lines, regexes)