fix(ssh): don't raise exception when default ssh keys can't be found

PR canonical#406 broke some end consumers/users of pycloudlib on systems where
1) ssh keys are not set in the pycloudlib.toml and the ssh key is later
set using the Cloud.use_key() method
2) no ssh keys exist at the default paths of '~/.ssh/id_rsa.pub' or
'~/.ssh/id_ed25519.pub'. This commit removes/reverts the error that
gets raised at the Cloud class instantation when those two cases
are true. There was no way for an end user to override/prevent
pycloudlib from erroring out besides for creating a fake ssh key
at one of the two default paths. Now, a warning is just logged instead,
restoring the flexibility pycloudlib preivously provided to end users
for setting their ssh keys.

Author: a-dubs

VERSION

@@ -1 +1 @@
-1!10.4.0
+1!10.5.0

pycloudlib/cloud.py

@@ -19,7 +19,7 @@
     PycloudlibError,
 )
 from pycloudlib.instance import BaseInstance
-from pycloudlib.key import KeyPair
+from pycloudlib.key import KeyPair, UnsetKeyPair
 from pycloudlib.util import (
     get_timestamped_tag,
     log_exception_list,
@@ -251,7 +251,12 @@ def use_key(self, public_key_path, private_key_path=None, name=None):
             name: name to reference key by
         """
         self._log.debug("using SSH key from %s", public_key_path)
-        self.key_pair = KeyPair(public_key_path, private_key_path, name)
+        self.config["public_key_path"] = public_key_path
+        if private_key_path:
+            self.config["private_key_path"] = private_key_path
+        if name:
+            self.config["key_name"] = name
+        self._get_ssh_keys()
 
     def _check_and_set_config(
         self,
@@ -325,10 +330,12 @@ def _get_ssh_keys(self) -> KeyPair:
                     public_key_path = pubkey
                     break
             if not public_key_path:
-                raise PycloudlibError(
+                self._log.warning(
                     "No public key path provided and no key found in default locations: "
-                    "'~/.ssh/id_rsa.pub' or '~/.ssh/id_ed25519.pub'"
+                    "'~/.ssh/id_rsa.pub' or '~/.ssh/id_ed25519.pub'. SSH key authentication will "
+                    "not be possible unless a key is later provided with the 'use_key' method."
                 )
+                return UnsetKeyPair()
         if not os.path.exists(os.path.expanduser(public_key_path)):
             raise PycloudlibError(f"Provided public key path '{public_key_path}' does not exist")
         if public_key_path not in possible_default_keys:

pycloudlib/errors.py

@@ -156,3 +156,11 @@ def __init__(self, tag: str, rules_failed: List[str]):
     def __str__(self) -> str:
         """Return string representation of the error."""
         return f"Tag '{self.tag}' failed the following rules: {', '.join(self.rules_failed)}"
+
+
+class UnsetSSHKeyError(PycloudlibException):
+    """Raised when a SSH key is unset and no default key can be found."""
+
+    def __str__(self) -> str:
+        """Return string representation of the error."""
+        return "No SSH key provided and no default key could be found."

pycloudlib/key.py

@@ -3,6 +3,8 @@
 
 import os
 
+from pycloudlib.errors import UnsetSSHKeyError
+
 
 class KeyPair:
     """Key Class."""
@@ -44,3 +46,31 @@ def public_key_content(self):
 
         """
         return open(self.public_key_path, encoding="utf-8").read()
+
+
+class UnsetKeyPair(KeyPair):
+    """
+    Placeholder for unset key pair when no key is provided and default keys can't be found.
+
+    This class is a subclass of KeyPair and is used to represent an unset key pair when no key is
+    provided in the pycloudlib.toml and default keys can't be found on the system.
+    """
+
+    def __init__(self):
+        """Initialize unset key pair."""
+        self.name = None
+        self.public_key_path = None
+        self.private_key_path = None
+
+    def __str__(self):
+        """Create string representation of class."""
+        return "UnsetKeyPair()"
+
+    @property
+    def public_key_content(self):
+        """
+        Raise a ValueError when trying to access the public key content for an unset key pair.
+
+        This
+        """
+        raise UnsetSSHKeyError("No public key content available for unset key pair")