devserver: Fix python3 problem when --portfile flag is passed.

And fix a few other things wrong too.

BUG=chromium:1031640
TEST=python3 ./devserver.py
TEST=python2 ./devserver.py
TEST=./devserver_integeration_test.py

Change-Id: Ib2aa17c8272c0e874b95ff19345c35fa003c1129
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/1954576
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
Auto-Submit: Amin Hassani <ahassani@chromium.org>
diff --git a/cherrypy_ext.py b/cherrypy_ext.py
index 2ebc189..33d7d6e 100644
--- a/cherrypy_ext.py
+++ b/cherrypy_ext.py
@@ -73,7 +73,7 @@
     port = self.get_port_from_httpserver()
     if not port:
       return
-    with open(self.portfile, 'wb') as f:
+    with open(self.portfile, 'w') as f:
       f.write(str(port))
     self.written = True
     self.bus.log('Port %r written to %r.' % (port, self.portfile))
@@ -101,7 +101,7 @@
         self.bus.log('Port file removed: %r.' % self.portfile)
       except (KeyboardInterrupt, SystemExit):
         raise
-      except:
+      except Exception:
         self.bus.log('Failed to remove port file: %r.' % self.portfile)