[Process] Make process tests more accurate on exception messages
minor #10419 [2.3][Process] Make process tests more accurate on exception messages (romainneutron)

This PR was merged into the 2.3 branch.

Discussion
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[2.3][Process] Make process tests more accurate on exception messages

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

I need exception message to be checked more accurately in my upcoming PR about windows.
I decided to make a separated PR as the other one will probably take some time before being merged

Commits
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1b1768a [Process] Make process tests more accurate on exception messages
[Process] Fix some unit tests that create the process object instead of delegate it to the implementation
minor #10421 [Process] Fix some unit tests that create the process object instead of delegate it to the implementation (romainneutron)

This PR was merged into the 2.3 branch.

Discussion
----------

[Process] Fix some unit tests that create the process object instead of delegate it to the implementation

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

This is a minor error ; creating the process must be delegated to the implementation

Commits
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227b85b [Process] Fix some unit tests that create the process object instead of delegate it to the implementation
[Process] Make Process::start non-blocking on Windows platform