Travis now uses Ubuntu 18.04 for builds

[SidRoberts]

Hello!

• Type: bug fix
• Link to issue: Travis build error during mysql-server install #14260

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines
• I have checked that another pull request for this purpose does not exist
• I wrote some tests for this PR
• [-] I have updated the relevant CHANGELOG
• [-] I have created a PR for the documentation about this change

Two important things of note:

• From OpenSSL 1.1.1, ciphers are lowercased
• Memcached::getAllKeys() appears to be broken from 1.4.23

I've tried to alter the code to work around these problems but I'd like someone with a fresh set of eyes to double check as I've been looking at this too long. 😜

[sergeyklay]

In general looks good to me

[sergeyklay]

It's a little bit confusing with the bugs in the getAllKeys() method

• One says it doesn't work with memcached 1.5+: getAllKeys returns an empty array on server 1.5+ php-memcached-dev/php-memcached#367
• One says it doesn't work with php-memcached before 3.0.1: Problem with new version memcached-1.4.24 php-memcached-dev/php-memcached#203 (comment)

[sergeyklay]

@SidRoberts Could you please change memcached version check to reflect this
See: php-memcached-dev/php-memcached#315

Make sure you use php-memcached extension >= 3.0.1 and memcached server >= 1.4.24

[SidRoberts]

I agree that this is very confusing. Currently Travis is using Memcached server 1.5.6 and Memcached extension 3.1.3. In theory, it should work but it doesn't.

I don't like the idea of a test doing version checking. I think the version checks should be in the getKeys() method and we should maybe implement code that actually gets all the keys instead of dealing with this mess.

How about keep the version check at >=1.2.24 for now, merge it and then deal with it later?

[SidRoberts]

Or, as a last ditch effort, what about bc0712e?

[CameronHall]

Looking good 👍

[sergeyklay]

Thank you