Raise new ContextError when configuration file is not found

3 files changed, 19 insertions, 6 deletions

diff --git a/buildstream/__init__.py b/buildstream/__init__.py
index ba8ed2951..80474548e 100644
--- a/buildstream/__init__.py
+++ b/buildstream/__init__.py
@@ -19,7 +19,7 @@
 #        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
 
 # Exceptions first
-from .exceptions import PluginError
+from .exceptions import PluginError, ContextError
 
 # Common stuff
 from .utils import dictionary_override
diff --git a/buildstream/exceptions.py b/buildstream/exceptions.py
index 55933fa4e..3c6483d88 100644
--- a/buildstream/exceptions.py
+++ b/buildstream/exceptions.py
@@ -20,9 +20,18 @@
 
 class PluginError(Exception):
     """Raised on plugin related errors.
-    
+
     This exception is raised when a plugin was not loaded correctly,
     or when the appropriate plugin could not be found to implement
     a given :class:`.Source` or :class:`.Element`
     """
     pass
+
+class ContextError(Exception):
+    """Raised while interpreting invocation context.
+
+    This exception is raised when creating the :class:`.InvocationContext`
+    when the user configuration is missing or malformed or if some
+    of the context is nonsensical
+    """
+    pass
diff --git a/buildstream/invocationcontext.py b/buildstream/invocationcontext.py
index 88b1d957a..31d7e5f01 100644
--- a/buildstream/invocationcontext.py
+++ b/buildstream/invocationcontext.py
@@ -22,6 +22,7 @@ import ruamel.yaml
 
 from .config import _site_info
 from .utils import dictionary_override
+from .exceptions import ContextError
 
 class InvocationContext():
     """Context of how BuildStream was invoked
@@ -68,7 +69,7 @@ class InvocationContext():
         ``$XDG_CONFIG_HOME/buildstream.yaml`` will be made.
         """
 
-        # Load em
+        # Load default config
         #
         defaults = self._load_config(_site_info['default_config'])
         if config:
@@ -84,8 +85,11 @@ class InvocationContext():
         self.ccachedir = defaults.get('ccachedir')
 
     def _load_config(self, filename):
-        with open(filename) as f:
-            text = f.read()
-            contents = ruamel.yaml.safe_load(text)
+        try:
+            with open(filename) as f:
+                text = f.read()
+                contents = ruamel.yaml.safe_load(text)
+        except FileNotFoundError as e:
+            raise ContextError("Failed to load configuration file %s" % filename) from e
 
         return contents