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Updating dependencies (including require-dev)
Package operations: 29 installs, 0 updates, 0 removals
  - Installing tornevall/tornelib-php-io (dev-develop/6.1 a1c0d06): Cloning a1c0d069b9 from cache
  - Installing sebastian/version (2.0.1): Loading from cache
  - Installing sebastian/resource-operations (2.0.1): Loading from cache
  - Installing sebastian/recursion-context (3.0.0): Loading from cache
  - Installing sebastian/object-reflector (1.1.1): Loading from cache
  - Installing sebastian/object-enumerator (3.0.3): Loading from cache
  - Installing sebastian/global-state (2.0.0): Loading from cache
  - Installing sebastian/exporter (3.1.2): Loading from cache
  - Installing sebastian/environment (4.2.3): Loading from cache
  - Installing sebastian/diff (3.0.2): Loading from cache
  - Installing sebastian/comparator (3.0.2): Loading from cache
  - Installing phpunit/php-timer (2.1.2): Loading from cache
  - Installing phpunit/php-text-template (1.2.1): Loading from cache
  - Installing phpunit/php-file-iterator (2.0.2): Loading from cache
  - Installing theseer/tokenizer (1.1.3): Loading from cache
  - Installing sebastian/code-unit-reverse-lookup (1.0.1): Loading from cache
  - Installing phpunit/php-token-stream (3.1.1): Loading from cache
  - Installing phpunit/php-code-coverage (6.1.4): Loading from cache
  - Installing doctrine/instantiator (1.3.0): Loading from cache
  - Installing symfony/polyfill-ctype (v1.14.0): Loading from cache
  - Installing webmozart/assert (1.7.0): Loading from cache
  - Installing phpdocumentor/reflection-common (2.0.0): Loading from cache
  - Installing phpdocumentor/type-resolver (1.0.1): Loading from cache
  - Installing phpdocumentor/reflection-docblock (5.0.0): Loading from cache
  - Installing phpspec/prophecy (v1.10.2): Loading from cache
  - Installing phar-io/version (2.0.1): Loading from cache
  - Installing phar-io/manifest (1.0.3): Loading from cache
  - Installing myclabs/deep-copy (1.9.5): Loading from cache
  - Installing phpunit/phpunit (7.5.20): Loading from cache
sebastian/global-state suggests installing ext-uopz (*)
phpunit/php-code-coverage suggests installing ext-xdebug (^2.6.0)
phpunit/phpunit suggests installing phpunit/php-invoker (^2.0)
phpunit/phpunit suggests installing ext-xdebug (*)
Writing lock file
Generating autoload files
Using version ^9.0 for phpunit/phpunit
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for sebastian/version (locked at 2.0.1) -> satisfiable by sebastian/version[2.0.1].
    - phpunit/phpunit 9.0.0 requires sebastian/version ^3.0 -> satisfiable by sebastian/version[3.0.0].
    - phpunit/phpunit 9.0.1 requires sebastian/version ^3.0 -> satisfiable by sebastian/version[3.0.0].
    - Conclusion: don't install sebastian/version 3.0.0
    - Installation request for phpunit/phpunit ^9.0 -> satisfiable by phpunit/phpunit[9.0.0, 9.0.1].


Installation failed, reverting ./composer.json to its original content.