Fix an error in cache:clear for Python 2.7

CHANGELOG.md

@@ -30,6 +30,7 @@
 - Fixed excluded files appearing in the `package_data` of the generated `setup.py`.
 - Fixed transitive directory dependencies installation.
 - Fixed file permissions for configuration and authentication files.
+- Fixed an error in `cache:clear` for Python 2.7.
 
 
 ## [0.11.5] - 2018-09-04

poetry/console/commands/cache/clear.py

@@ -45,7 +45,7 @@ class CacheClearCommand(Command):
                     "{} caches".format(parts[0])
                 )
 
-            if not os.path.exists(cache_dir):
+            if not os.path.exists(str(cache_dir)):
                 self.line("No cache entries for {}".format(parts[0]))
                 return 0