Merge pull request #2019 from bdarnell/colorama-fix

log: Fix color logging detection

tornado/log.py

@@ -54,18 +54,21 @@
 
 
 def _stderr_supports_color():
-    color = False
-    if hasattr(sys.stderr, 'isatty') and sys.stderr.isatty():
-        if curses:
-            try:
+    try:
+        if hasattr(sys.stderr, 'isatty') and sys.stderr.isatty():
+            if curses:
                 curses.setupterm()
                 if curses.tigetnum("colors") > 0:
-                    color = True
-            except Exception:
-                pass
-        elif colorama:
-            color = True
-    return color
+                    return True
+            elif colorama:
+                if sys.stderr is getattr(colorama.initialise, 'wrapped_stderr',
+                                         object()):
+                    return True
+    except Exception:
+        # Very broad exception handling because it's always better to
+        # fall back to non-colored logs than to break at startup.
+        pass
+    return False
 
 
 def _safe_unicode(s):
@@ -146,12 +149,12 @@ def __init__(self, fmt=DEFAULT_FORMAT, datefmt=DEFAULT_DATE_FORMAT,
                 for levelno, code in colors.items():
                     self._colors[levelno] = unicode_type(curses.tparm(fg_color, code), "ascii")
                 self._normal = unicode_type(curses.tigetstr("sgr0"), "ascii")
-            elif sys.stderr is getattr(colorama, 'wrapped_stderr', object()):
+            else:
+                # If curses is not present (currently we'll only get here for
+                # colorama on windows), assume hard-coded ANSI color codes.
                 for levelno, code in colors.items():
                     self._colors[levelno] = '\033[2;3%dm' % code
                 self._normal = '\033[0m'
-            else:
-                raise RuntimeError("No supported color terminal library")
         else:
             self._normal = ''