Upgrading Drupal

Hoping someone can help us out - we're trying to update core to 8.3 using composer (from within Homestead/Vagrant VM running on Windows). We have three dev PCs and two updated fine, but one refuses to cooperate;

Running composer install displays a warning for every module:
Class Drupal\Core\Composer\Composer is not autoloadable, cannot call post-package-install script

And then when it gets to drupal/core the entire process fails with a RuntimeException. It seems to download ok (100%) but then fails with this message:

I have blog in drupal 7.
My all content are blog content using drupal 7 blog core module
If I want to upgrade, do I need to install blog module for D8 ?

Hi! I have a non-profit website, www.bridesmaidshare.com. Last week I realized that the site was down. I contacted my provider Dreamhost and they said it didn't look like anything on their end was wrong but saw that the site had recently been updated - which I don't think I did.
Now when I go to the site it says "Welcome to your new Drupal website!" and asks me to login, but doesn't accept my login info.

Any support is highly appreciated. Thank you!

Hello
I have an drupal 7 site. In this site I have blog content type. I want to upgrade to it in drupal 8

I have followed everything as per drupals official steps. Enabled migration, ui and upgraded. During Upgrading it showed blog destination missing. But I continued.

Now my site can show all blog title as was in drupal7. Also url of that title is ok. But problem is body.
In the body it is blank. Even I tried to edit, still it blank.

Hi,

Since I've applied the 8.3.1 upgrade to my site, every time I paste from word (using the paste from word in CKEditor) the text now retains font-size and font-family styles in containing spans.

If I save the content and then edit and save again then it eventually loses the font styling but keeps the spans.

This behaviour is new since 8.2.x. Any suggestions?

Thanks

Hello,
I am getting MYSQL error when trying to migrate from D7 to D8:
Specified key was too long; max key length is 1000 bytes: CREATE TABLE {migrate_map_58f7923f89f06} ( `source_ids_hash` VARCHAR(64) NOT NULL COMMENT 'Hash of source ids. Used as primary key', `sourceid1` VARCHAR(255) NOT NULL, `sourceid2` VARCHAR(255) NOT NULL, `sourceid3` VARCHAR(255) NOT NULL,
...etc

I can see this is some migration table that is just being created and I am not sure why the keys in it are too long.