pip 升级后 CDH hue 启动失败

问题

一次 pip 升级后，发现 CDH6.1 运行出现警告（当时并不知道是因为升级 pip 导致的）
查询日志 /var/log/cloudera-scm-server/cloudera-scm-server.log 没有有价值的错误
于是重启集群，hue 仍然重启失败
错误只有：

ERROR CommandPusher:com.cloudera.cmf.model.DbCommand: Command 2142(Restart) has completed. finalstate:FINISHED, success:false, msg:Failed to start all the services.

于是删除 hue 服务重新添加
在测试连接数据库时，连接失败。得到报错：

2019-06-27 11:47:20,073 INFO CommandPusher:com.cloudera.cmf.service.AbstractOneOffHostCommand: Unsuccessful 'HueTestDatabaseConnection'
2019-06-27 11:47:20,074 INFO CommandPusher:com.cloudera.cmf.service.AbstractDbConnectionTestCommand: Command exited with code: 1
2019-06-27 11:47:20,074 INFO CommandPusher:com.cloudera.cmf.service.AbstractDbConnectionTestCommand: + '[' ldaptest = is_db_alive ']'
+ exec /opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/bin/hue is_db_alive
Traceback (most recent call last):
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/bin/hue", line 9, in <module>
    from pkg_resources import load_entry_point
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3126, in <module>
    @_call_aside
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3110, in _call_aside
    f(*args, **kwargs)
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3139, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 572, in _build_master
    ws = cls()
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 565, in __init__
    self.add_entry(entry)
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 621, in add_entry
    for dist in find_distributions(entry, True):
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1968, in find_on_path
    for dist in factory(fullpath):
  File "/opt/cloudera/parcel-repo/CDH-6.1.0-1.cdh6.1.0.p0.770702/lib/hue/build/env/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2030, in distributions_from_metadata
    if len(os.listdir(path)) == 0:
OSError: [Errno 13] Permission denied: '/usr/lib/python2.7/site-packages/pip-19.1.1.dist-info'

2019-06-27 11:47:20,074 ERROR CommandPusher:com.cloudera.cmf.model.DbCommand: Command 2332(HueTestDatabaseConnection) has completed. finalstate:FINISHED, success:false, msg:Unexpected error. Unable to verify database connection.

可以看出是对 pip-19.1.1.dist-info 的权限不够
（由于刚升级 pip 到 pip19，因此想到是 pip 升级导致 hue 没有足够权限，启动失败）

解决方法

找到 pip-19.1.1.dist-info 所在路径，赋权限755。继续添加 hue，成功。

chmod 755 -R pip-19.1.1.dist-info