Bug 1564799 - Use sphinx.util.logging instead of app.info(). r=ahal

Differential Revision: https://phabricator.services.mozilla.com/D37539

--HG--
extra : moz-landing-system : lando

tools/docs/moztreedocs/__init__.py

@@ -21,6 +21,8 @@ build = MozbuildObject.from_environment(cwd=here)
 
 MAIN_DOC_PATH = os.path.join(build.topsrcdir, 'tools', 'docs')
 
+logger = sphinx.util.logging.getLogger(__name__)
+
 
 @memoize
 def read_build_config(docdir):
@@ -82,12 +84,12 @@ class _SphinxManager(object):
         """Generate/stage documentation."""
         self.staging_dir = os.path.join(app.outdir, '_staging')
 
-        app.info('Reading Sphinx metadata from build configuration')
+        logger.info('Reading Sphinx metadata from build configuration')
         self.trees, self.python_package_dirs = read_build_config(app.srcdir)
 
-        app.info('Staging static documentation')
+        logger.info('Staging static documentation')
         self._synchronize_docs()
-        app.info('Generating Python API documentation')
+        logger.info('Generating Python API documentation')
         self._generate_python_api_docs()
 
     def _generate_python_api_docs(self):