* Always generate a new key pair if the private key doesn't exist (#597)
This commit updates `KeypairBackend._should_generate()` to first check
if the original private key named by the `path` argument exists, and
return True if it does not. This brings the code in line with
the documentation, which says that a new key will always be generated if
the key file doesn't already exist.
As an alternative to the approach implemented here, I also considered
only modifying the condition in the `fail` branch of the if statement,
but I thought that would not map as cleanly to the behavior specified in
the documentation, so doing it the way I did should make it easier to
check that the code is doing the right thing just by looking at it.
I also considered doing something to make the logic more similar to
`PrivateKeyBackend.needs_regeneration()` (the openssl version of this
functionality), because the two are supposed to be acting the same way,
but I thought that'd be going beyond the scope of just fixing this bug.
If it'd be useful to make both methods work the same way, someone can
refactor the code in a future commit.
* Test different regenerate values with nonexistent keys
This commit changes the test task that generates new keys to use each of
the different values for the `regenerate` argument, which will ensure
that the module is capable of generating a key when no previous key
exists regardless of the value of `regenerate`. Previously, the task
would always run with the `partial_idempotence` value, and that obscured
a bug (#597) that would occur when it was set to `fail`. The bug was
fixed in the previous commit.
ce3299f106