[ReflectionException] Class Magento\Framework\Serialize\Serializer\Json does not exist

[skashish]

I used following commands on Magento EE 2.1.7 to install sample data.
OS - Ubuntu 14.04

cd <Magento_root_directory>
git clone https://github.com/magento/magento2-sample-data.git ./sample-data

php -f ./sample-data/dev/tools/build-sample-data.php -- --ce-source="."
All symlinks you can see at files:
<Magento_root_directory>/sample-data/dev/tools/exclude.log

After that, When I ran php bin/magento setup:upgrade, I get

[ReflectionException]                                             
Class Magento\Framework\Serialize\Serializer\Json does not exist

[skashish]

Also, I'm unable to uninstall. When I run
php -f ./sample-data/dev/tools/build-sample-data.php - --command=unlink --ce-source="."

I get Expected folder not found.

[AlessandroStaffolani]

Same error, tried to install sample data after installing magento 2.1.7, I cloned sample-data repo from github, I run the command php -f ./sample-data/dev/tools/build-sample-data.php -- --ce-source="." then on upgrade I get this error:

[ReflectionException] Class Magento\Framework\Serialize\Serializer\Json does not exist

[akhan522]

I get an error saying "Class Magento\Framework\Serialize\Serializer\Json does not exist" when I try to create an attribute

[kandy]

Please try use 2.1-develop branch of sample data for 2.1.7 Magento version

[ptkfenelon]

Hi, i'm sorry for my English.

I was having the same problem in Magento 2.1.8.
I solved the problem by cloning the latest version of the repository (https://github.com/magento/magento2.git) and copying the 'Serialize' package to version 2.1.8.

Path: <magento_path>/lib/internal/Magento/Framework/Serialize/