diff --git a/cps/gdriveutils.py b/cps/gdriveutils.py
index b26f24d0..b4036083 100644
--- a/cps/gdriveutils.py
+++ b/cps/gdriveutils.py
@@ -201,7 +201,7 @@ def backupCalibreDbAndOptionalDownload(drive, f=None):
     metaDataFile="'%s' in parents and title = 'metadata.db' and trashed = false" % getEbooksFolderId()
 
     fileList = drive.ListFile({'q': metaDataFile}).GetList()
- 
+
     databaseFile=fileList[0]
 
     if f:
@@ -353,7 +353,7 @@ def getChangeById (drive, change_id):
     if not drive:
         drive=getDrive()
     if drive.auth.access_token_expired:
-        drive.auth.Refresh() 
+        drive.auth.Refresh()
     # Print a single Change resource information.
     #
     # Args:
diff --git a/cps/helper.py b/cps/helper.py
index 5cf64372..8522d336 100755
--- a/cps/helper.py
+++ b/cps/helper.py
@@ -81,7 +81,7 @@ def make_mobi(book_id, calibrepath):
     file_path = os.path.join(calibrepath, book.path, data.name)
     if os.path.exists(file_path + u".epub"):
         p = subprocess.Popen((kindlegen + " \"" + file_path + u".epub\" ").encode(sys.getfilesystemencoding()),
-                             shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
+                             stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         # Poll process for new output until finished
         while True:
             nextline = p.stdout.readline()
@@ -252,7 +252,7 @@ def get_valid_filename(value, replace_whitespace=True):
         value=value.replace(u'ß',u'ss')
         value = unicodedata.normalize('NFKD', value)
         re_slugify = re.compile('[\W\s-]', re.UNICODE)
-        if type(value) is str: #Python3 str, Python2 unicode
+        if isinstance(value, str): #Python3 str, Python2 unicode
             value = re_slugify.sub('', value).strip()
         else:
             value = unicode(re_slugify.sub('', value).strip())
@@ -300,7 +300,7 @@ def update_dir_stucture(book_id, calibrepath):
 def update_dir_structure_gdrive(book_id):
     db.session.connection().connection.connection.create_function("title_sort", 1, db.title_sort)
     book = db.session.query(db.Books).filter(db.Books.id == book_id).first()
-    
+
     authordir = book.path.split('/')[0]
     new_authordir = get_valid_filename(book.authors[0].name)
     titledir = book.path.split('/')[1]
diff --git a/cps/static/js/main.js b/cps/static/js/main.js
index 7b409c0d..d759a3b8 100644
--- a/cps/static/js/main.js
+++ b/cps/static/js/main.js
@@ -13,7 +13,7 @@ $(function() {
         $.ajax({
         dataType: "json",
         url: window.location.pathname+"/../../get_updater_status",
-        success: function(data) {
+        success(data) {
             // console.log(data.status);
             $("#UpdateprogressDialog #Updatecontent").html(updateText[data.status]);
             if (data.status >6){
diff --git a/cps/web.py b/cps/web.py
index 592240c1..c81df370 100755
--- a/cps/web.py
+++ b/cps/web.py
@@ -272,14 +272,9 @@ def load_user_from_header(header_val):
         return user
     return
 
-
 def check_auth(username, password):
     user = ub.session.query(ub.User).filter(ub.User.nickname == username).first()
-    if user and check_password_hash(user.password, password):
-        return True
-    else:
-        return False
-
+    return bool(user and check_password_hash(user.password, password))
 
 def authenticate():
     return Response(
@@ -1239,11 +1234,10 @@ def stats():
         kindlegen = os.path.join(vendorpath, u"kindlegen")
     versions['KindlegenVersion'] = _('not installed')
     if os.path.exists(kindlegen):
-        p = subprocess.Popen(kindlegen, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
-                             stdin=subprocess.PIPE)
+        p = subprocess.Popen(kindlegen, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         p.wait()
         for lines in p.stdout.readlines():
-            if type(lines) is bytes:
+            if isinstance(lines, bytes):
                 lines = lines.decode('utf-8')
             if re.search('Amazon kindlegen\(', lines):
                 versions['KindlegenVersion'] = lines