CENTOS7 system upgrade Yum update error no module named Pycurl

after the CENTOS7 upgrade, run the Yum update results as follows:
]# Yum Update
There was a problem importing one of the Python modules
Required to run Yum. The error leading to this problem was:

No module named Pycurl

Install a package which provides this module, or
Verify the module is installed correctly.

It ' s possible that the above module doesn ' t match the
Current version of Python, which is:
2.7.5 (default, May 3 2017, 07:55:04)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-14)]

If You cannot solve this problem yourself and go to
The Yum FAQ at:
Http://yum.baseurl.org/wiki/Faq

Install Pycurl:

Pip Install Pycurl

Collecting Pycurl
Using Cached pycurl-7.43.0.1.tar.gz
Installing collected Packages:pycurl
Running setup.py Install for pycurl ... done
Successfully installed pycurl-7.43.0.1

Test upgrade, run Yum update
]# Yum Updae
There was a problem importing one of the Python modules
Required to run Yum. The error leading to this problem was:

Pycurl:libcurl Link-time SSL Backend (NSS) is different from Compile-time SSL backend (None/other)

Install a package which provides this module, or
Verify the module is installed correctly.

It ' s possible that the above module doesn ' t match the
Current version of Python, which is:
2.7.5 (default, May 3 2017, 07:55:04)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-14)]

If You cannot solve this problem yourself and go to
The Yum FAQ at:
Http://yum.baseurl.org/wiki/Faq

Online to find a lot of information, not a suitable, check another computer with the same configuration, found that the version of Pycurl is 7.19.0. Uninstall Pycurl7.43.0,pip Uninstall Pycurl. Reinstall the specified version: Pip install pycurl==7.19.0
]# pip Install pycurl==7.19.0
Collecting pycurl==7.19.0
Using Cached pycurl-7.19.0.tar.gz
Installing collected Packages:pycurl
Running setup.py Install for pycurl ... done
Successfully installed pycurl-7.19.0
Test upgrade, run Yum update
]# Yum Update-y
Loaded Plugins:amazon-id, Fastestmirror, rhui-lb, Search-disabled-repos
Loading mirror speeds from cached hostfile

• city-fan.org:www.city-fan.org
• Epel:ny-mirrors.evowise.com
• Rhui-region-client-config-server-7: rhui2-cds02.us-east-1.aws.ce.redhat.com
• Rhui-region-rhel-server-releases:rhui2-cds02.us-east-1.aws.ce.redhat.com
• Rhui-region-rhel-server-rh-common:rhui2-cds02.us-east-1.aws.ce.redhat.com
  No packages marked for update
  The command was executed successfully .

PostScript, when you start to install Pycurl, you can only install manually. Because it is a cloud host, directly download the same version of the ISO image file (3 minutes to download about 5G files), mount and copy 2 rpm files to the local system. LIBCURL-7.29.0-42.EL7.X86_64.RPM, libcurl-devel-7.29.0-42.el7.x86_64.rpm

Due to package dependencies, individual installation fails, go to rpm folder, Run command installation, RPM-UVH *.rpm--nodeps--force

CENTOS7 system upgrade Yum update error no module named Pycurl