如何在ubuntu上更新高级打包工具（apt）？ gnutls_handshake（）失败：握手失败

Question

我正在尝试更新“ apt”，但出现以下错误。如何更新“ apt”？

Err https://qgis.org trusty/main Sources                                       
  gnutls_handshake() failed: Handshake failed
Err https://qgis.org trusty/main amd64 Packages                                
  gnutls_handshake() failed: Handshake failed
Err https://qgis.org trusty/main i386 Packages                                 
  gnutls_handshake() failed: Handshake failed


W: Failed to fetch https://qgis.org/debian/dists/trusty/main/source    
/Sources  gnutls_handshake() failed: Handshake failed

W: Failed to fetch https://qgis.org/debian/dists/trusty/main/binary- 
amd64/Packages  gnutls_handshake() failed: Handshake failed

W: Failed to fetch https://qgis.org/debian/dists/trusty/main/binary- 
i386/Packages  gnutls_handshake() failed: Handshake failed
E: Some index files failed to download. They have been ignored, or old 
ones used instead.