diff --git a/pythonforandroid/logger.py b/pythonforandroid/logger.py
index 75fee40d1a..b05d137f57 100644
--- a/pythonforandroid/logger.py
+++ b/pythonforandroid/logger.py
@@ -1,4 +1,3 @@
-
 import logging
 import os
 import re
@@ -16,7 +15,7 @@
     stderr = codecs.getwriter('utf8')(stderr)
 
 if six.PY2:
-    unistr = unicode
+    unistr = unicode  # noqa F821
 else:
     unistr = str
 
diff --git a/pythonforandroid/recipes/android/src/android/mixer.py b/pythonforandroid/recipes/android/src/android/mixer.py
index 4ac224a790..3f85c6352e 100644
--- a/pythonforandroid/recipes/android/src/android/mixer.py
+++ b/pythonforandroid/recipes/android/src/android/mixer.py
@@ -196,10 +196,10 @@ def __init__(self, what):
         self.serial = str(sound_serial)
         sound_serial += 1
 
-        if isinstance(what, file):
+        if isinstance(what, file):  # noqa F821
             self.file = what
         else:
-            self.file = file(os.path.abspath(what), "rb")
+            self.file = file(os.path.abspath(what), "rb")  # noqa F821
 
         sounds[self.serial] = self
 
diff --git a/pythonforandroid/util.py b/pythonforandroid/util.py
index cc9d94a616..75e56bde63 100644
--- a/pythonforandroid/util.py
+++ b/pythonforandroid/util.py
@@ -15,11 +15,6 @@
 
 IS_PY3 = sys.version_info[0] >= 3
 
-if IS_PY3:
-    unistr = str
-else:
-    unistr = unicode
-
 
 class WgetDownloader(FancyURLopener):
     version = ('Wget/1.17.1')
@@ -106,7 +101,7 @@ def sync(self):
                 json.dump(self.data, fd, ensure_ascii=False)
         else:
             with io.open(self.filename, 'w', encoding='utf-8') as fd:
-                fd.write(unicode(json.dumps(self.data, ensure_ascii=False)))
+                fd.write(unicode(json.dumps(self.data, ensure_ascii=False)))  # noqa F821
 
 
 def which(program, path_env):
@@ -128,20 +123,3 @@ def is_exe(fpath):
                 return exe_file
 
     return None
-
-
-def get_directory(filename):
-    '''If the filename ends with a recognised file extension, return the
-    filename without this extension.'''
-    if filename.endswith('.tar.gz'):
-        return basename(filename[:-7])
-    elif filename.endswith('.tgz'):
-        return basename(filename[:-4])
-    elif filename.endswith('.tar.bz2'):
-        return basename(filename[:-8])
-    elif filename.endswith('.tbz2'):
-        return basename(filename[:-5])
-    elif filename.endswith('.zip'):
-        return basename(filename[:-4])
-    info('Unknown file extension for {}'.format(filename))
-    exit(1)
diff --git a/tox.ini b/tox.ini
index 56261dcd03..ea0c63985f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,4 +12,4 @@ ignore =
     E111, E114, E115, E116, E202, E121, E123, E124, E225, E126, E127, E128,
     E129, E201, E203, E221, E226, E231, E241, E251, E261, E265, E266, E271,
     E302, E303, E305, E401, E402, E501, E502, E703, E722, E741, F403,
-    F812, F821, F841, F811, W291, W292, W293, W391, W503
+    F812, F841, F811, W291, W292, W293, W391, W503