env vars passed to `spawn` are not visible in child process

[saukap]

Describe the bug
wexpect.spawn takes an optional parameter env but doesn't propagate those env vars it to the child process.

To Reproduce
Steps to reproduce the behavior:

Run the following script:

p = wexpect.spawn('cmd', env={'NAME': 'VALUE'})
p.expect('>')
p.sendline('echo %NAME%')
p.expect('>')
print(p.before.splitlines()[1])

Observed output: %NAME%

Expected behavior
VALUE is output

Screenshots
If applicable, add screenshots to help explain your problem.

Environment:

• Windows 10
• 3.10
• 4.0.0

Additional context
None