base and buildbots: certificate issues

[mascguy (Christopher Nielsen)]

It looks like we're experiencing certificate issues, both on the buildbots, as well as locally. It's not clear whether this is related to the certificate authorities, our own certs, or something else.

On multiple buildbots, I'm seeing different variations of certificate validation errors. And this is occurring across multiple mirrors; both our own, as well as those from 3rd-parties:

​https://build.macports.org/builders/ports-10.10_x86_64-builder/builds/156470/steps/install-port/logs/stdio

--->  Attempting to fetch rrdtool-1.7.2.tar.gz from https://distfiles.macports.org/rrdtool
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
DEBUG: Fetching distfile failed: SSL certificate problem: Invalid certificate chain

​https://build.macports.org/builders/ports-10.6_x86_64-builder/builds/74262/steps/install-port/logs/stdio

--->  Attempting to fetch rrdtool-1.7.2.tar.gz from http://oss.oetiker.ch/rrdtool/pub/
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
DEBUG: Fetching distfile failed: error:1407742E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert protocol version

​https://build.macports.org/builders/ports-10.13_x86_64-builder/builds/124365/steps/install-port/logs/stdio

--->  Attempting to fetch rrdtool-1.7.2.tar.gz from http://oss.oetiker.ch/rrdtool/pub/
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
DEBUG: Fetching distfile failed: SSL certificate problem: certificate has expired

These appear to be sporadic, as they aren't occurring across-the-board.

In addition, I'm also seeing certificate errors locally, though those are also sporadic.