Copy manifests and DLLs on Windows.

Hopefully fixes issue pypa#294
<pypa#294>,
at least it seems to work for me.

Generalises the code for copying multiple files from the source to the
destination, so it should be easier to read, and easier to add more files
to the list in future.

virtualenv.py

@@ -47,7 +47,7 @@
 except ImportError:
     import configparser as ConfigParser
 
-join = os.path.join
+from os.path import join
 py_version = 'python%s.%s' % (sys.version_info[0], sys.version_info[1])
 
 is_jython = sys.platform.startswith('java')
@@ -1276,6 +1276,9 @@ def install_python(home_dir, lib_dir, inc_dir, bin_dir, site_packages, clear):
             os.unlink(pyd_pth)
 
     if sys.executable != py_executable:
+        source_dir = os.path.dirname(sys.executable)
+        dest_dir = os.path.dirname(py_executable)
+
         ## FIXME: could I just hard link?
         executable = sys.executable
         if sys.platform == 'cygwin' and os.path.exists(executable + '.exe'):
@@ -1286,36 +1289,31 @@ def install_python(home_dir, lib_dir, inc_dir, bin_dir, site_packages, clear):
         shutil.copyfile(executable, py_executable)
         make_exe(py_executable)
         if sys.platform == 'win32' or sys.platform == 'cygwin':
-            pythonw = os.path.join(os.path.dirname(sys.executable), 'pythonw.exe')
-            if os.path.exists(pythonw):
-                logger.info('Also created pythonw.exe')
-                shutil.copyfile(pythonw, os.path.join(os.path.dirname(py_executable), 'pythonw.exe'))
-            python_d = os.path.join(os.path.dirname(sys.executable), 'python_d.exe')
-            python_d_dest = os.path.join(os.path.dirname(py_executable), 'python_d.exe')
-            if os.path.exists(python_d):
-                logger.info('Also created python_d.exe')
-                shutil.copyfile(python_d, python_d_dest)
-            elif os.path.exists(python_d_dest):
-                logger.info('Removed python_d.exe as it is no longer at the source')
-                os.unlink(python_d_dest)
-            # we need to copy the DLL to enforce that windows will load the correct one.
-            # may not exist if we are cygwin.
-            py_executable_dll = 'python%s%s.dll' % (
-                sys.version_info[0], sys.version_info[1])
-            py_executable_dll_d = 'python%s%s_d.dll' % (
-                sys.version_info[0], sys.version_info[1])
-            pythondll = os.path.join(os.path.dirname(sys.executable), py_executable_dll)
-            pythondll_d = os.path.join(os.path.dirname(sys.executable), py_executable_dll_d)
-            pythondll_d_dest = os.path.join(os.path.dirname(py_executable), py_executable_dll_d)
-            if os.path.exists(pythondll):
-                logger.info('Also created %s' % py_executable_dll)
-                shutil.copyfile(pythondll, os.path.join(os.path.dirname(py_executable), py_executable_dll))
-            if os.path.exists(pythondll_d):
-                logger.info('Also created %s' % py_executable_dll_d)
-                shutil.copyfile(pythondll_d, pythondll_d_dest)
-            elif os.path.exists(pythondll_d_dest):
-                logger.info('Removed %s as the source does not exist' % pythondll_d_dest)
-                os.unlink(pythondll_d_dest)
+            files_to_sync = set(('pythonw.exe', 'python_d.exe',
+                'python%s%s.dll' % (sys.version_info[0], sys.version_info[1]),
+                'python%s%s_d.dll' % (sys.version_info[0], sys.version_info[1]),
+                ))
+
+            # Copy any manifests and DLLs we can find
+            import glob
+
+            for dir in (source_dir, dest_dir):
+                for pattern in ('*.manifest', '*.dll'):
+                    for found_file in glob.iglob(join(dir, pattern)):
+                        files_to_sync.add(os.path.basename(found_file))
+
+            for filename in files_to_sync:
+                source_file = join(source_dir, filename)
+                dest_file = join(dest_dir, filename)
+
+                if os.path.exists(source_file):
+                    logger.info('Also created %s' % filename)
+                    shutil.copyfile(source_file, dest_file)
+                elif os.path.exists(dest_file):
+                    logger.info('Removed %s as it is no longer at the source' %
+                        filename)
+                    os.unlink(dest_file)
+
         if is_pypy:
             # make a symlink python --> pypy-c
             python_executable = os.path.join(os.path.dirname(py_executable), 'python')