client: corrected fallback action and url handler register

src/nsi/installer/win_install.py

@@ -145,9 +145,16 @@ def main():
                     ('circle\\URL Protocol', ""),
                     ('circle\\DefaultIcon', args.location+"cloud.ico"),
                     ('circle\\shell', {'open': {
-                        'command': r'"%s\pythonw.exe"' % sys.exec_prefix
-                        + r' "%s' % args.location
-                        + r'\cloud.py" "%1"'}})])
+                        'command': (
+                            "\"%(prefix)s\pythonw.exe\""
+                            " \"%(location)s"
+                            "cloud.py\" " % {
+                                'prefix': sys.exec_prefix,
+                                'location': args.location
+                            }
+                        + r'"%1"')
+                    }})
+                ])
                 custom_protocol_register(custom_protocol)
             except:
                 print "Error! URL Protocol handler installation aborted!"