code: def build(self):
          
  
          if self.exists:
              self._build(
                  'requirements',
                  self.requirements_last_modified,
                  'pip install -U -r %s' % self.requirements_file
              )
              try:
                  self._build(
                      'requirements (dev)',
                      self.dev_requirements_last_modified,
                      'pip install -U -r %s' % self.dev_requirements_file
                  )
              except Exception as e:
                  if 'No such file' not in str(e):
                      raise e
                  self.stdout.write(
                      style.yellow('Could not find dev requirements')
                  )
              try:
                  self._build(
                      'requirements (local)',
                      self.local_requirements_last_modified,
                      'pip install -U -r %s' % self.local_requirements_file
                  )
              except Exception as e:
                  if 'No such file' not in str(e):
                      raise e
                  self.stdout.write(
                      style.yellow('Could not find local requirements')
                  )
              self._build(
                  'application',
                  self.setup_last_modified,
                  'python %s develop' % self.setup_file
              )
docs: Builds the app in the app's environment.
  
          Only builds if the build is out-of-date and is non-empty.
          Builds in 3 stages: requirements, dev requirements, and app.
          pip is used to install requirements, and setup.py is used to
          install the app itself.
  
          Raises:
              ValidationError if the app fails to build.