diff --git a/nhentai/dojinshi.py b/nhentai/dojinshi.py
index 945aeea..a7b100e 100644
--- a/nhentai/dojinshi.py
+++ b/nhentai/dojinshi.py
@@ -40,5 +40,5 @@ if __name__ == '__main__':
     test.show()
     try:
         test.download()
-    except Exception, e:
+    except Exception as e:
         print 'Exception: %s' % str(e)
\ No newline at end of file
diff --git a/nhentai/downloader.py b/nhentai/downloader.py
index fc054f6..334ea90 100644
--- a/nhentai/downloader.py
+++ b/nhentai/downloader.py
@@ -34,20 +34,20 @@ class Downloader(object):
                 else:
                     for chunk in response.iter_content(2048):
                         f.write(chunk)
-        except (os.error, IOError), e:
+        except requests.HTTPError as e:
             if not retried:
                 logger.error('Error: %s, retrying' % str(e))
                 return self._download(url=url, folder=folder, filename=filename, retried=True)
             else:
                 return None
-        except Exception, e:
+        except Exception as e:
             logger.critical('CRITICAL: %s' % str(e))
-            raise e
+            return None
         return url
 
     def _download_callback(self, request, result):
         if not result:
-            logger.critical('Too many network errors occurred, please check your connection.')
+            logger.critical('Too many errors occurred, quit.')
             raise SystemExit
         logger.log(15, '%s download successfully' % result)
 
@@ -62,7 +62,7 @@ class Downloader(object):
             logger.warn('Path \'%s\' not exist.' % folder)
             try:
                 os.mkdir(folder)
-            except os.error, e:
+            except EnvironmentError as e:
                 logger.critical('Error: %s' % str(e))
                 raise SystemExit
         else:
diff --git a/nhentai/logger.py b/nhentai/logger.py
index 7d62582..157bf1f 100644
--- a/nhentai/logger.py
+++ b/nhentai/logger.py
@@ -75,7 +75,7 @@ class ColorizingStreamHandler(logging.StreamHandler):
             if fd is not None:
                 fd = fd()
 
-                if fd in (1, 2): # stdout or stderr
+                if fd in (1, 2):  # stdout or stderr
                     h = ctypes.windll.kernel32.GetStdHandle(-10 - fd)
 
             while parts:
@@ -97,11 +97,11 @@ class ColorizingStreamHandler(logging.StreamHandler):
                             elif 30 <= p <= 37:
                                 color |= self.nt_color_map[p - 30]
                             elif p == 1:
-                                color |= 0x08 # foreground intensity on
-                            elif p == 0: # reset to default color
+                                color |= 0x08  # foreground intensity on
+                            elif p == 0:  # reset to default color
                                 color = 0x07
                             else:
-                                pass # error condition ignored
+                                pass  # error condition ignored
 
                         ctypes.windll.kernel32.SetConsoleTextAttribute(h, color)
 
@@ -127,7 +127,7 @@ class ColorizingStreamHandler(logging.StreamHandler):
                     prefix = ""
 
                 message = "%s%s" % (prefix, ''.join((self.csi, ';'.join(params),
-                                   'm', message, self.reset)))
+                                    'm', message, self.reset)))
 
         return message
 
diff --git a/nhentai/parser.py b/nhentai/parser.py
index 32477cf..3b70828 100644
--- a/nhentai/parser.py
+++ b/nhentai/parser.py
@@ -17,7 +17,7 @@ def dojinshi_parser(id):
 
     try:
         response = requests.get(url).content
-    except Exception, e:
+    except Exception as e:
         logger.critical('%s%s' % tuple(e.message))
         sys.exit()