Add isatty method to LazyWriter.

gunicorn/glogging.py

@@ -87,6 +87,9 @@ class LazyWriter(object):
     def flush(self):
         self.open().flush()
 
+    def isatty(self):
+        return bool(self.fileobj and self.fileobj.isatty())
+
 class SafeAtoms(dict):
 
     def __init__(self, atoms):

tests/test_005-lazywriter-isatty.py

@@ -0,0 +1,13 @@
+import sys
+
+from gunicorn.glogging import LazyWriter
+
+
+def test_lazywriter_isatty():
+    orig = sys.stdout
+    sys.stdout = LazyWriter('test.log')
+    try:
+        sys.stdout.isatty()
+    except AttributeError:
+        raise AssertionError("LazyWriter has no attribute 'isatty'")
+    sys.stdout = orig