The "more" cmd varies across Windows flavors, sometimes adding stray

newlines at the start or end.  Fiddle test_popen2 and popen2._test() to
tolerate this.  Also change all "assert"s in these tests to raise
explicit exceptions, so that python -O doesn't render them useless.
Also, in case of error, make the msg display the reprs of what we
wrote and what we read, so we can tell exactly why it's failing.

1 files changed, 16 insertions, 7 deletions

diff --git a/Lib/popen2.py b/Lib/popen2.py
index e0f2880e75..64c34d4cb5 100644
--- a/Lib/popen2.py
+++ b/Lib/popen2.py
@@ -143,16 +143,20 @@ else:
 
 def _test():
     cmd  = "cat"
-    teststr = "abc\n"
-    resultstr = teststr
+    teststr = "ab cd\n"
     if os.name == "nt":
         cmd = "more"
-        resultstr = "\n" + resultstr
+    # "more" doesn't act the same way across Windows flavors,
+    # sometimes adding an extra newline at the start or the
+    # end.  So we strip whitespace off both ends for comparison.
+    expected = teststr.strip()
     print "testing popen2..."
     r, w = popen2(cmd)
     w.write(teststr)
     w.close()
-    assert r.read() == resultstr
+    got = r.read()
+    if got.strip() != expected:
+        raise ValueError("wrote %s read %s" % (`teststr`, `got`))
     print "testing popen3..."
     try:
         r, w, e = popen3([cmd])
@@ -160,11 +164,16 @@ def _test():
         r, w, e = popen3(cmd)
     w.write(teststr)
     w.close()
-    assert r.read() == resultstr
-    assert e.read() == ""
+    got = r.read()
+    if got.strip() != expected:
+        raise ValueError("wrote %s read %s" % (`teststr`, `got`))
+    got = e.read()
+    if got:
+        raise ValueError("unexected %s on stderr" % `got`)
     for inst in _active[:]:
         inst.wait()
-    assert not _active
+    if _active:
+        raise ValueError("_active not empty")
     print "All OK"
 
 if __name__ == '__main__':