code cleanup and error improvement for hashi_vault (ansible#17824)

Use standard import error handling.
Make error messages more specific.
Use more python idiomatic code.

lib/ansible/plugins/lookup/hashi_vault.py

@@ -39,6 +39,12 @@
 from ansible.errors import AnsibleError
 from ansible.plugins.lookup import LookupBase
 
+HAS_HVAC = False
+try:
+    import hvac
+    HAS_HVAC = True
+except ImportError:
+    HAS_HVAC = False
 
 ANSIBLE_HASHI_VAULT_ADDR = 'http://127.0.0.1:8200'
 
@@ -48,17 +54,17 @@
 
 class HashiVault:
     def __init__(self, **kwargs):
-        try:
-            import hvac
-        except ImportError:
-            raise AnsibleError("Please pip install hvac to use this module")
 
         self.url = kwargs.get('url', ANSIBLE_HASHI_VAULT_ADDR)
 
+        self.token = kwargs.get('token')
+        if self.token is None:
+            raise AnsibleError("No Hashicorp Vault Token specified for hash_vault lookup")
+
         # split secret arg, which has format 'secret/hello:value' into secret='secret/hello' and secret_field='value'
         s = kwargs.get('secret')
         if s is None:
-            raise AnsibleError("No secret specified")
+            raise AnsibleError("No secret specified for hashi_vault lookup")
 
         s_f = s.split(':')
         self.secret = s_f[0]
@@ -97,22 +103,20 @@ def __init__(self, **kwargs):
 
             self.client = hvac.Client(url=self.url, token=self.token)
 
-        if self.client.is_authenticated():
-            pass
-        else:
-            raise AnsibleError("Invalid authentication credentials specified")
+        if not self.client.is_authenticated():
+            raise AnsibleError("Invalid Hashicorp Vault Token Specified for hashi_vault lookup")
 
     def get(self):
         data = self.client.read(self.secret)
 
         if data is None:
-            raise AnsibleError("The secret %s doesn't seem to exist" % self.secret)
+            raise AnsibleError("The secret %s doesn't seem to exist for hashi_vault lookup" % self.secret)
 
         if self.secret_field == '':  # secret was specified with trailing ':'
             return data['data']
 
         if self.secret_field not in data['data']:
-            raise AnsibleError("The secret %s does not contain the field '%s'. " % (self.secret, self.secret_field))
+            raise AnsibleError("The secret %s does not contain the field '%s'. for hashi_vault lookup" % (self.secret, self.secret_field))
 
         return data['data'][self.secret_field]
 
@@ -134,15 +138,18 @@ def auth_ldap(self, **kwargs):
 
 class LookupModule(LookupBase):
     def run(self, terms, variables, **kwargs):
+        if not HAS_HVAC:
+            raise AnsibleError("Please pip install hvac to use the hashi_vault lookup module.")
+
         vault_args = terms[0].split(' ')
         vault_dict = {}
         ret = []
 
         for param in vault_args:
             try:
                 key, value = param.split('=')
-            except ValueError as e:
-                raise AnsibleError("hashi_vault plugin needs key=value pairs, but received %s" % terms)
+            except ValueError:
+                raise AnsibleError("hashi_vault lookup plugin needs key=value pairs, but received %s" % terms)
             vault_dict[key] = value
 
         vault_conn = HashiVault(**vault_dict)