dvc: logger: use colorama to colorize output

Colors help readability, especially in verbose mode.
Current color map:

	Debug:   Blue
	Info:    White
	Warning: Yellow
	Error:   Red

dvc/logger.py

@@ -1,5 +1,8 @@
+import sys
 import logging
 
+import colorama
+
 class Logger(object):
     DEFAULT_LEVEL = logging.INFO
 
@@ -10,6 +13,12 @@ class Logger(object):
         'error': logging.ERROR
     }
 
+    COLOR_MAP = {
+        'debug': colorama.Fore.BLUE,
+        'warn': colorama.Fore.YELLOW,
+        'error': colorama.Fore.RED
+    }
+
     logging.basicConfig(stream=sys.stdout, format='%(message)s', level=DEFAULT_LEVEL)
 
     _logger = logging.getLogger('dvc')
@@ -26,18 +35,29 @@ class Logger(object):
     def be_verbose():
         Logger._logger.setLevel(logging.DEBUG)
 
+    @staticmethod
+    def colorize(msg, typ):
+        header = ''
+        footer = ''
+
+        if sys.stdout.isatty():
+            header = Logger.COLOR_MAP.get(typ.lower(), '')
+            footer = colorama.Style.RESET_ALL
+
+        return u'{}{}{}'.format(header, msg, footer)
+
     @staticmethod
     def error(msg):
-        return Logger._logger.error(msg)
+        return Logger._logger.error(Logger.colorize(msg, 'error'))
 
     @staticmethod
     def warn(msg):
-        return Logger._logger.warn(msg)
+        return Logger._logger.warn(Logger.colorize(msg, 'warn'))
 
     @staticmethod
     def debug(msg):
-        return Logger._logger.debug(msg)
+        return Logger._logger.debug(Logger.colorize(msg, 'debug'))
 
     @staticmethod
     def info(msg):
-        return Logger._logger.info(msg) 
+        return Logger._logger.info(Logger.colorize(msg, 'info'))

requirements.txt

@@ -84,3 +84,4 @@ simplegeneric==0.8.1
 six==1.10.0
 traitlets==4.3.2
 wcwidth==0.1.7
+colorama

setup.py

@@ -90,6 +90,7 @@ install_requires = [
     'six==1.10.0',
     'traitlets==4.3.2',
     'wcwidth==0.1.7',
+    'colorama',
 ]
 
 if platform.system() == 'Darwin':