test-install: embed wix namespace for Python 2.6 compatibility

According to doc, the syntax is "{uri}tag".

https://docs.python.org/2.7/library/xml.etree.elementtree.html#parsing-xml-with-namespaces

tests/test-install.t

@@ -1,113 +1,113
 hg debuginstall
   $ hg debuginstall
   checking encoding (ascii)...
   checking Python executable (*) (glob)
   checking Python version (2.*) (glob)
   checking Python lib (*lib*)... (glob)
   checking installed modules (*mercurial)... (glob)
   checking templates (*mercurial?templates)... (glob)
   checking commit editor...
   checking username...
   no problems detected
 
 hg debuginstall with no username
   $ HGUSER= hg debuginstall
   checking encoding (ascii)...
   checking Python executable (*) (glob)
   checking Python version (2.*) (glob)
   checking Python lib (*lib*)... (glob)
   checking installed modules (*mercurial)... (glob)
   checking templates (*mercurial?templates)... (glob)
   checking commit editor...
   checking username...
    no username supplied
    (specify a username in your configuration file)
   1 problems detected, please check your install!
   [1]
 
 path variables are expanded (~ is the same as $TESTTMP)
   $ mkdir tools
   $ touch tools/testeditor.exe
 #if execbit
   $ chmod 755 tools/testeditor.exe
 #endif
   $ hg debuginstall --config ui.editor=~/tools/testeditor.exe
   checking encoding (ascii)...
   checking Python executable (*) (glob)
   checking Python version (*) (glob)
   checking Python lib (*lib*)... (glob)
   checking installed modules (*mercurial)... (glob)
   checking templates (*mercurial?templates)... (glob)
   checking commit editor...
   checking username...
   no problems detected
 
 #if test-repo
   $ cat >> wixxml.py << EOF
   > import os, subprocess, sys
   > import xml.etree.ElementTree as ET
   > 
   > # MSYS mangles the path if it expands $TESTDIR
   > testdir = os.environ['TESTDIR']
   > ns = {'wix' : 'http://schemas.microsoft.com/wix/2006/wi'}
   > 
   > def directory(node, relpath):
   >     '''generator of files in the xml node, rooted at relpath'''
-  >     dirs = node.findall('./wix:Directory', ns)
+  >     dirs = node.findall('./{%(wix)s}Directory' % ns)
   > 
   >     for d in dirs:
   >         for subfile in directory(d, relpath + d.attrib['Name'] + '/'):
   >             yield subfile
   > 
-  >     files = node.findall('./wix:Component/wix:File', ns)
+  >     files = node.findall('./{%(wix)s}Component/{%(wix)s}File' % ns)
   > 
   >     for f in files:
   >         yield relpath + f.attrib['Name']
   > 
   > def hgdirectory(relpath):
   >     '''generator of tracked files, rooted at relpath'''
   >     hgdir = "%s/../mercurial" % (testdir)
   >     args = ['hg', '--cwd', hgdir, 'files', relpath]
   >     proc = subprocess.Popen(args, stdout=subprocess.PIPE,
   >                             stderr=subprocess.PIPE)
   >     output = proc.communicate()[0]
   > 
   >     slash = '/'
   >     for line in output.splitlines():
   >         if os.name == 'nt':
   >             yield line.replace(os.sep, slash)
   >         else:
   >             yield line
   > 
   > tracked = [f for f in hgdirectory(sys.argv[1])]
   > 
   > xml = ET.parse("%s/../contrib/wix/%s.wxs" % (testdir, sys.argv[1]))
   > root = xml.getroot()
-  > dir = root.find('.//wix:DirectoryRef', ns)
+  > dir = root.find('.//{%(wix)s}DirectoryRef' % ns)
   > 
   > installed = [f for f in directory(dir, '')]
   > 
   > print('Not installed:')
   > for f in sorted(set(tracked) - set(installed)):
   >     print('  %s' % f)
   > 
   > print('Not tracked:')
   > for f in sorted(set(installed) - set(tracked)):
   >     print('  %s' % f)
   > EOF
 
   $ python wixxml.py help
   Not installed:
     help/common.txt
     help/hg.1.txt
     help/hgignore.5.txt
     help/hgrc.5.txt
     help/internals/bundles.txt
     help/internals/changegroups.txt
   Not tracked:
 
   $ python wixxml.py templates
   Not installed:
   Not tracked:
 
 #endif