Do not allow unicode-related exceptions inside logger

Fixes #421

powerline/__init__.py

@@ -7,33 +7,14 @@ import logging
 
 from powerline.colorscheme import Colorscheme
 from powerline.lib.config import ConfigLoader
+from powerline.lib.unicode import safe_unicode
 
 from threading import Lock, Event
 
-try:
-	from __builtin__ import unicode
-except ImportError:
-	unicode = str  # NOQA
-
 
 DEFAULT_SYSTEM_CONFIG_DIR = None
 
 
-def safe_unicode(s):
-	'''Return unicode instance without raising an exception.
-	'''
-	try:
-		try:
-			return unicode(s)
-		except UnicodeDecodeError:
-			try:
-				return unicode(s, 'utf-8')
-			except TypeError:
-				return unicode(str(s), 'utf-8')
-	except Exception as e:
-		return safe_unicode(e)
-
-
 class FailedUnicode(unicode):
 	'''Builtin ``unicode`` (``str`` in python 3) subclass indicating fatal 
 	error.
@@ -69,7 +50,7 @@ class PowerlineLogger(object):
 		prefix = self.ext + ((':' + prefix) if prefix else '')
 		if args or kwargs:
 			msg = msg.format(*args, **kwargs)
-		msg = prefix + ':' + msg
+		msg = prefix + ':' + safe_unicode(msg)
 		key = attr + ':' + prefix
 		if msg != self.last_msgs.get(key):
 			getattr(self.logger, attr)(msg)

powerline/lib/unicode.py

@@ -1,5 +1,9 @@
 # vim:fileencoding=utf-8:noet
 
+
+from locale import getpreferredencoding
+
+
 try:
 	from __builtin__ import unicode
 except ImportError:
@@ -7,7 +11,35 @@ except ImportError:
 
 
 def u(s):
+	'''Return unicode instance assuming UTF-8 encoded string.
+	'''
 	if type(s) is unicode:
 		return s
 	else:
 		return unicode(s, 'utf-8')
+
+
+def safe_unicode(s):
+	'''Return unicode instance without raising an exception.
+
+	Order of assumptions:
+	* ASCII string or unicode object
+	* UTF-8 string
+	* Object with __str__() or __repr__() method that returns UTF-8 string or 
+	  unicode object (depending on python version)
+	* String in locale.getpreferredencoding() encoding
+	* If everything failed use safe_unicode on last exception with which 
+	  everything failed
+	'''
+	try:
+		try:
+			return unicode(s)
+		except UnicodeDecodeError:
+			try:
+				return unicode(s, 'utf-8')
+			except TypeError:
+				return unicode(str(s), 'utf-8')
+			except UnicodeDecodeError:
+				return unicode(s, getpreferredencoding())
+	except Exception as e:
+		return safe_unicode(e)