diff --git a/wakatime/languages/unknown.py b/wakatime/languages/unknown.py
index 9e9724e..bfd1cb0 100644
--- a/wakatime/languages/unknown.py
+++ b/wakatime/languages/unknown.py
@@ -12,7 +12,6 @@
 import os
 
 from . import TokenParser
-from ..compat import u
 
 
 FILES = {
diff --git a/wakatime/log.py b/wakatime/log.py
index b70d21b..7cec4a2 100644
--- a/wakatime/log.py
+++ b/wakatime/log.py
@@ -30,7 +30,6 @@ class CustomEncoder(json.JSONEncoder):
         try:
             encoded = super(CustomEncoder, self).default(obj)
         except UnicodeDecodeError:
-            encoding = sys.getfilesystemencoding()
             obj = u(obj)
             encoded = super(CustomEncoder, self).default(obj)
         return encoded
@@ -63,7 +62,7 @@ class JsonFormatter(logging.Formatter):
         return CustomEncoder().encode(data)
 
     def formatException(self, exc_info):
-        return exec_info[2].format_exc()
+        return sys.exec_info[2].format_exc()
 
 
 def set_log_level(logger, args):
diff --git a/wakatime/project.py b/wakatime/project.py
index 56a8657..949a76d 100644
--- a/wakatime/project.py
+++ b/wakatime/project.py
@@ -10,7 +10,6 @@
 """
 
 import logging
-import os
 
 from .projects.git import Git
 from .projects.mercurial import Mercurial
diff --git a/wakatime/projects/base.py b/wakatime/projects/base.py
index d1af823..60c3ac4 100644
--- a/wakatime/projects/base.py
+++ b/wakatime/projects/base.py
@@ -10,7 +10,6 @@
 """
 
 import logging
-import os
 
 
 log = logging.getLogger('WakaTime')
diff --git a/wakatime/projects/wakatime.py b/wakatime/projects/wakatime.py
index fa33f4f..41ec0d6 100644
--- a/wakatime/projects/wakatime.py
+++ b/wakatime/projects/wakatime.py
@@ -34,7 +34,7 @@ class WakaTime(BaseProject):
                 with open(self.config, 'r', encoding='utf-8') as fh:
                     self._project_name = u(fh.readline().strip())
                     self._project_branch = u(fh.readline().strip())
-            except IOError as e:
+            except IOError:
                 log.exception("Exception:")
 
             return True
diff --git a/wakatime/stats.py b/wakatime/stats.py
index 50ff4a4..830a39b 100644
--- a/wakatime/stats.py
+++ b/wakatime/stats.py
@@ -65,7 +65,7 @@ def guess_language_from_extension(extension):
         if extension in EXTENSIONS:
             return EXTENSIONS[extension]
         if extension.lower() in EXTENSIONS:
-            return mapping[EXTENSIONS.lower()]
+            return EXTENSIONS[extension.lower()]
     return None