Bugfix #15 - Remove use of not exist exception.

[plumthedev]

Description

Use InvalidArgumentException instead of not exist exception of Dotenv

Motivation and context

Why is this change required? What problem does it solve?

Fixes #15

How has this been tested?

No tests needed here

Screenshots (if appropriate)

Types of changes

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• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

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