docs(cli): add PyYAML requirement noticeci-output-option

Fixes #606

2 files changed, 21 insertions, 6 deletions

diff --git a/docs/cli.rst b/docs/cli.rst
index 220f079..2051d03 100644
--- a/docs/cli.rst
+++ b/docs/cli.rst
@@ -157,6 +157,11 @@ These options must be defined before the mandatory arguments.
 ``--output``, ``-o``
     Output format. Defaults to a custom format. Can also be ``yaml`` or ``json``.
 
+    **Notice:**
+
+        The `PyYAML package <https://pypi.org/project/PyYAML/>`_ is required to use the yaml output option.
+        You need to install it separately using ``pip install PyYAML``
+
 ``--fields``, ``-f``
     Comma-separated list of fields to display (``yaml`` and ``json`` output
     formats only).  If not used, all the object fields are displayed.
diff --git a/gitlab/v4/cli.py b/gitlab/v4/cli.py
index a876f9e..242874d 100644
--- a/gitlab/v4/cli.py
+++ b/gitlab/v4/cli.py
@@ -302,14 +302,24 @@ class JSONPrinter(object):
 
 class YAMLPrinter(object):
     def display(self, d, **kwargs):
-        import yaml  # noqa
-        print(yaml.safe_dump(d, default_flow_style=False))
+        try:
+            import yaml  # noqa
+            print(yaml.safe_dump(d, default_flow_style=False))
+        except ImportError:
+            exit("PyYaml is not installed.\n"
+                 "Install it with `pip install PyYaml` "
+                 "to use the yaml output feature")
 
     def display_list(self, data, fields, **kwargs):
-        import yaml  # noqa
-        print(yaml.safe_dump(
-            [get_dict(obj, fields) for obj in data],
-            default_flow_style=False))
+        try:
+            import yaml  # noqa
+            print(yaml.safe_dump(
+                [get_dict(obj, fields) for obj in data],
+                default_flow_style=False))
+        except ImportError:
+            exit("PyYaml is not installed.\n"
+                 "Install it with `pip install PyYaml` "
+                 "to use the yaml output feature")
 
 
 class LegacyPrinter(object):