diff --git a/serial/aio.py b/serial/aio.py
index 5756be0..85a1bb8 100644
--- a/serial/aio.py
+++ b/serial/aio.py
@@ -278,7 +278,7 @@
     def _set_write_buffer_limits(self, high=None, low=None):
         """Ensure consistent write-buffer limits."""
         if high is None:
-            high = 64*1024 if low is None else 4*low
+            high = 64 * 1024 if low is None else 4 * low
         if low is None:
             low = high // 4
         if not high >= low >= 0:
diff --git a/serial/rfc2217.py b/serial/rfc2217.py
index c8afa95..5e3cbe3 100644
--- a/serial/rfc2217.py
+++ b/serial/rfc2217.py
@@ -410,7 +410,7 @@
         if self.is_open:
             raise SerialException("Port is already open.")
         try:
-            self._socket = socket.create_connection(self.from_url(self.portstr), timeout=5) # XXX good value?
+            self._socket = socket.create_connection(self.from_url(self.portstr), timeout=5)  # XXX good value?
             self._socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
         except Exception as msg:
             self._socket = None
diff --git a/serial/urlhandler/protocol_loop.py b/serial/urlhandler/protocol_loop.py
index cce9f7d..daf2415 100644
--- a/serial/urlhandler/protocol_loop.py
+++ b/serial/urlhandler/protocol_loop.py
@@ -99,7 +99,10 @@
         """extract host and port from an URL string"""
         parts = urlparse.urlsplit(url)
         if parts.scheme != "loop":
-            raise SerialException('expected a string in the form "loop://[?logging={debug|info|warning|error}]": not starting with loop:// (%r)' % (parts.scheme,))
+            raise SerialException(
+                'expected a string in the form '
+                '"loop://[?logging={debug|info|warning|error}]": not starting '
+                'with loop:// (%r)' % (parts.scheme,))
         try:
             # process options now, directly altering self
             for option, values in urlparse.parse_qs(parts.query, True).items():
@@ -111,7 +114,9 @@
                 else:
                     raise ValueError('unknown option: %r' % (option,))
         except ValueError as e:
-            raise SerialException('expected a string in the form "loop://[?logging={debug|info|warning|error}]": %s' % e)
+            raise SerialException(
+                'expected a string in the form '
+                '"loop://[?logging={debug|info|warning|error}]": %s' % e)
 
     #  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -