gistfile1.txt

 bootstrap-panels$ composer require symfony/serializer
You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug
Using version ^3.3 for symfony/serializer
./composer.json has been updated
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Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Conclusion: don't install symfony/serializer v3.3.2
    - Conclusion: don't install symfony/serializer v3.3.1
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.0].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.1].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.2].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.3].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.4].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.5].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.6].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.7].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.8].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.9].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.9].
    - symfony/serializer v3.3.0 conflicts with symfony/symfony[v3.2.9].
    - Installation request for symfony/serializer ^3.3 -> satisfiable by symfony/serializer[v3.3.0, v3.3.1, v3.3.2].
    - Installation request for symfony/symfony 3.2.* -> satisfiable by symfony/symfony[v3.2.0, v3.2.1, v3.2.2, v3.2.3, v3.2.4, v3.2.5, v3.2.6, v3.2.7, v3.2.8, v3.2.9].