Fixed Issue celery#6017:

Changed the default paths for logs and pid files to be '/var/log/celery' and '/var/run/celery'
Handled by creating the respective paths if not exist.
Used os.makedir(path,if_exists=True)
Updated the .travis.yml file.

.travis.yml

@@ -48,21 +48,27 @@ matrix:
 
   - python: '3.8'
     env: TOXENV=flake8
+    before_install: sudo mkdir /var/log/celery && sudo mkdir /var/run/celery && sudo chown travis /var/log/celery && sudo chown travis /var/run/celery
     stage: lint
   - python: '3.8'
     env: TOXENV=apicheck
+    before_install: sudo mkdir /var/log/celery && sudo mkdir /var/run/celery && sudo chown travis /var/log/celery && sudo chown travis /var/run/celery
     stage: lint
   - python: '3.8'
     env: TOXENV=configcheck
+    before_install: sudo mkdir /var/log/celery && sudo mkdir /var/run/celery && sudo chown travis /var/log/celery && sudo chown travis /var/run/celery
     stage: lint
   - python: '3.8'
     env: TOXENV=bandit
+    before_install: sudo mkdir /var/log/celery && sudo mkdir /var/run/celery && sudo chown travis /var/log/celery && sudo chown travis /var/run/celery
     stage: lint
   - python: '3.8'
     env: TOXENV=pydocstyle
+    before_install: sudo mkdir /var/log/celery && sudo mkdir /var/run/celery && sudo chown travis /var/log/celery && sudo chown travis /var/run/celery
     stage: lint
   - python: '2.7'
     env: TOXENV=flakeplus
+    before_install: sudo mkdir /var/log/celery && sudo mkdir /var/run/celery && sudo chown travis /var/log/celery && sudo chown travis /var/run/celery
     stage: lint
   - python: pypy2.7-7.3
     env: TOXENV=pypy

celery/apps/multi.py

@@ -140,8 +140,8 @@ def __init__(self, name,
 
     def _annotate_with_default_opts(self, options):
         options['-n'] = self.name
-        self._setdefaultopt(options, ['--pidfile', '-p'], '%n.pid')
-        self._setdefaultopt(options, ['--logfile', '-f'], '%n%I.log')
+        self._setdefaultopt(options, ['--pidfile', '-p'], '/var/run/celery/%n.pid')
+        self._setdefaultopt(options, ['--logfile', '-f'], '/var/log/celery/%n%I.log')
         self._setdefaultopt(options, ['--executable'], sys.executable)
         return options
 
@@ -151,6 +151,8 @@ def _setdefaultopt(self, d, alt, value):
                 return d[opt]
             except KeyError:
                 pass
+        path_list = value.split("/")
+        os.makedirs("/".join(path_list[0:-1]), exist_ok=True)
         return d.setdefault(alt[0], value)
 
     def _prepare_expander(self):