Make Certbot runnable on Windows (#6296)

* Add and use a compatibility layer to allow certbot to be run on windows.

* Fix path comparison

* Corrections on compat and util for tests

* Less intrusive way to parse prefix in webroot plugin working for both linux and windows.

* Disable pylint import-error for some optional imports in compat.py

* Ensure path is normalized before prefixes are generated in webroot plugin

* Same prefixes in linux and windows, in fact root path is not needed in webroot plugin

* Check that user has administrative rights before continuing on windows (necessary for symlink creation)

* More straightforward way to test administrative rights on windows

* Try to resolve import error in travis ci

* OK. We go for full introspection to trick the ci.

* Move the administrative rights control to the certbot entrypoint

* Add comment for a really non trivial code.

* Allow some commands to be run on a shell without admin rights

* Avoid races conditions on windows for lock files

* Add sphinx doc to the compat functions.

* Remove irrelevant Windows error in the lock mechanism.

* Some corrections on compat

certbot/account.py

@@ -17,6 +17,7 @@ import zope.component
 from acme import fields as acme_fields
 from acme import messages
 
+from certbot import compat
 from certbot import constants
 from certbot import errors
 from certbot import interfaces
@@ -140,7 +141,7 @@ class AccountFileStorage(interfaces.AccountStorage):
     """
     def __init__(self, config):
         self.config = config
-        util.make_or_verify_dir(config.accounts_dir, 0o700, os.geteuid(),
+        util.make_or_verify_dir(config.accounts_dir, 0o700, compat.os_geteuid(),
                                    self.config.strict_permissions)
 
     def _account_dir_path(self, account_id):
@@ -323,7 +324,7 @@ class AccountFileStorage(interfaces.AccountStorage):
 
     def _save(self, account, acme, regr_only):
         account_dir_path = self._account_dir_path(account.id)
-        util.make_or_verify_dir(account_dir_path, 0o700, os.geteuid(),
+        util.make_or_verify_dir(account_dir_path, 0o700, compat.os_geteuid(),
                                 self.config.strict_permissions)
         try:
             with open(self._regr_path(account_dir_path), "w") as regr_file: