Add Windows as supported operating system

This change is necessary in order to use the project's
update-requirements.py script when preparing the environment on the
Hyper-V compute nodes used in the Hyper-V CI. Using the mentioned script
will set the latest requirements in nova, neutron, manila, etc.,
reducing the CI's amount of failures caused by outdated requirements.

Including Microsoft Windows as a supported operating system on this
project. Also, we update the edit-constraints.py and project.py
files to support os.rename() of Windows.

On Windows, os.rename() will create a file with the source
name, without deleting the initial file first.

Example of a traceback:

 Traceback (most recent call last):
   File "C:\Python27\Scripts\edit-constraints-script.py", line 9, in
 <module>
     load_entry_point('openstack.requirements==0.0.1.dev2497',
 'console_scripts', 'edit-constraints')()
   File
 "C:\Python27\lib\site-packages\openstack_requirements\cmds\edit_constraint.py",
 line 74, in main
     os.rename(args[0] + '.tmp', args[0])
 WindowsError: [Error 183] Cannot create a file when that file already exists

This could be easily solved by removing the file before the rename.

Proposed fix:
Add before "os.rename(args[0] + '.tmp', args[0])" the line "os.remove(args[0])"
in edit_constraint.py
Add before "os.rename(tmpname, fullname)" the line "os.remove(fullname)"
in project.py
Add "Operating System :: Microsoft :: Windows" in setup.cfg

DocImpact: Added Windows as a supported OS in setup.cfg
Change-Id: If123a65fd8d49d5c67a1db16827a9617ce520dba
Signed-off-by: Costin Galan <cgalan@cloudbasesolutions.com>

openstack_requirements/cmds/edit_constraint.py

@@ -71,5 +71,7 @@ def main(argv=None, stdout=None):
     out = requirement.to_content(out_reqs, prefix=False)
     with open(args[0] + '.tmp', 'wt') as f:
         f.write(out)
+    if os.path.exists(args[0]):
+        os.remove(args[0])
     os.rename(args[0] + '.tmp', args[0])
     return 0

openstack_requirements/project.py

@@ -105,7 +105,7 @@ def _safe_read(project, filename, output=None):
     if output is None:
         output = project
     try:
-        path = project['root'] + '/' + filename
+        path = os.path.join(project['root'], filename)
         with io.open(path, 'rt', encoding="utf-8") as f:
             output[filename] = f.read()
     except IOError as e:
@@ -166,10 +166,12 @@ def write(project, actions, stdout, verbose, noop=False):
         elif type(action) is File:
             if noop:
                 continue
-            fullname = project['root'] + '/' + action.filename
+            fullname = os.path.join(project['root'], action.filename)
             tmpname = fullname + '.tmp'
             with open(tmpname, 'wt') as f:
                 f.write(action.content)
+            if os.path.exists(fullname):
+                os.remove(fullname)
             os.rename(tmpname, fullname)
         elif type(action) is StdOut:
             stdout.write(action.message)

setup.cfg

@@ -12,6 +12,7 @@ classifier =
     Intended Audience :: System Administrators
     License :: OSI Approved :: Apache Software License
     Operating System :: POSIX :: Linux
+    Operating System :: Microsoft :: Windows
     Programming Language :: Python
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7