8 – Composer update failure

Contents of composer.json:

{
    "name": "drupal-composer/drupal-project",
    "description": "Project template for Drupal 8 projects with composer",
    "type": "project",
    "license": "GPL-2.0-or-later",
    "authors": [
        {
            "name": "",
            "role": ""
        }
    ],
    "repositories": [
        {
            "type": "composer",
            "url": "https://packages.drupal.org/8"
        }
    ],
    "require": {
        "chi-teck/drupal-code-generator": "dev-master",
        "composer/installers": "^1.2",
        "cweagans/composer-patches": "^1.6.5",
        "drupal-composer/drupal-scaffold": "^2.5",
        "drupal/admin_toolbar": "^1.25",
        "drupal/chosen": "^2.6",
        "drupal/ckeditor_a11ychecker": "^1.0",
        "drupal/ckeditor_balloonpanel": "^1.1",
        "drupal/ckeditor_div_manager": "^1.0",
        "drupal/ckeditor_liststyle": "^1.3",
        "drupal/ckeditor_uploadimage": "^1.7",
        "drupal/console": "^1.0.2",
        "drupal/core": "^8.6",
        "drupal/devel": "^2.0",
        "drupal/entity_reference_integrity": "^1.0@RC",
        "drupal/eva": "^1.3",
        "drupal/imce": "^1.7",
        "drupal/inline_entity_form": "^1.0@RC",
        "drupal/ldap": "^3.0@beta",
        "drupal/markup": "^1.0@beta",
        "drupal/masquerade": "^2.0@beta",
        "drupal/migrate_plus": "^4.1",
        "drupal/migrate_source_csv": "^2.2",
        "drupal/migrate_tools": "^4.1",
        "drupal/module_filter": "^3.1",
        "drupal/readonly_field_widget": "^1.2",
        "drupal/serial": "1.x-dev",
        "drupal/taxonomy_access_fix": "^2.6",
        "drupal/token": "^1.5",
        "drupal/uuid_extra": "1.x-dev",
        "drush/drush": "^9.0.0",
        "egulias/email-validator": "^1.0",
        "vlucas/phpdotenv": "^2.4",
        "webflo/drupal-core-require-dev": "^8.6",
        "webflo/drupal-finder": "^1.0.0",
        "webmozart/path-util": "^2.3"
    },
    "require-dev": {
    },
    "conflict": {
        "drupal/drupal": "*"
    },
    "minimum-stability": "dev",
    "prefer-stable": true,
    "config": {
        "sort-packages": true
    },
    "autoload": {
        "classmap": [
            "scripts/composer/ScriptHandler.php"
        ],
        "files": ["load.environment.php"]
    },
    "scripts": {
        "pre-install-cmd": [
            "DrupalProject\composer\ScriptHandler::checkComposerVersion"
        ],
        "pre-update-cmd": [
            "DrupalProject\composer\ScriptHandler::checkComposerVersion"
        ],
        "post-install-cmd": [
            "DrupalProject\composer\ScriptHandler::createRequiredFiles"
        ],
        "post-update-cmd": [
            "DrupalProject\composer\ScriptHandler::createRequiredFiles"
        ]
    },
    "extra": {
        "patchLevel": {
            "drupal/core": "-p2"
        },
        "installer-paths": {
            "web/core": ["type:drupal-core"],
            "web/libraries/{$name}": ["type:drupal-library"],
            "web/modules/contrib/{$name}": ["type:drupal-module"],
            "web/profiles/contrib/{$name}": ["type:drupal-profile"],
            "web/themes/contrib/{$name}": ["type:drupal-theme"],
            "drush/Commands/{$name}": ["type:drupal-drush"]
        },
        "drupal-scaffold": {
            "initial": {
                ".editorconfig": "../.editorconfig",
                ".gitattributes": "../.gitattributes"
            }
        }
    }
}