Update build from database at __exit__

When an exception happens and it's handled by __exit__ our Build in
the database is not updated and it stay in 'Installing' forever. So,
when something bad happens we force a call to `update_build` with the
FINISHED state

Attempt to fix #3285

Author: humitos

.gitignore

@@ -43,3 +43,4 @@ private_*
 readthedocs/htmlcov
 tags
 .python-version
+*.pyo

readthedocs/doc_builder/environments.py

@@ -556,6 +556,7 @@ def __exit__(self, exc_type, exc_value, tb):
                       exc_info=True)
         self.container = None
         self.build['state'] = BUILD_STATE_FINISHED
+        self.update_build(BUILD_STATE_FINISHED)
         log.info(LOG_TEMPLATE
                  .format(project=self.project.slug,
                          version=self.version.slug,