Capture errors on trying to open file URIs

4 files changed, 41 insertions, 13 deletions

diff --git a/mammoth/docx/files.py b/mammoth/docx/files.py
index bde488d..dc5146e 100644
--- a/mammoth/docx/files.py
+++ b/mammoth/docx/files.py
@@ -19,17 +19,17 @@ class Files(object):
             pass
     
     def open(self, uri):
-        if _is_absolute(uri):
-            return contextlib.closing(urlopen(uri))
-        elif self._base is not None:
-            try:
+        try:
+            if _is_absolute(uri):
+                return contextlib.closing(urlopen(uri))
+            elif self._base is not None:
                 return open(os.path.join(self._base, uri), "rb")
-            except IOError as error:
-                message = "could not open external image '{0}' from document directory '{1}'\n{2}".format(
-                    uri, self._base, str(error))
-                raise InvalidFileReferenceError(message)
-        else:
-            raise InvalidFileReferenceError("could not find external image '{0}', fileobj has no name".format(uri))
+            else:
+                raise InvalidFileReferenceError("could not find external image '{0}', fileobj has no name".format(uri))
+        except IOError as error:
+            message = "could not open external image: '{0}' (document directory: '{1}')\n{2}".format(
+                uri, self._base, str(error))
+            raise InvalidFileReferenceError(message)
 
 
 def _is_absolute(url):
diff --git a/tests/docx/files_tests.py b/tests/docx/files_tests.py
index c1e15dc..56dc69a 100644
--- a/tests/docx/files_tests.py
+++ b/tests/docx/files_tests.py
@@ -1,7 +1,7 @@
 from nose.tools import istest, assert_equal
 
-from mammoth.docx.files import Files
-from ..testing import test_path
+from mammoth.docx.files import Files, InvalidFileReferenceError
+from ..testing import test_path, assert_raises
 
 
 @istest
@@ -23,3 +23,22 @@ def can_open_files_with_relative_uri():
         assert_equal(bytes, type(contents))
         with open(test_path("tiny-picture.png"), "rb") as source_file:
             assert_equal(source_file.read(), contents)
+
+
+@istest
+def error_is_raised_if_relative_uri_cannot_be_opened():
+    files = Files("/tmp")
+    error = assert_raises(InvalidFileReferenceError, lambda: files.open("not-a-real-file.png"))
+    expected_message = (
+        "could not open external image: 'not-a-real-file.png' (document directory: '/tmp')\n" +
+        "[Errno 2] No such file or directory: '/tmp/not-a-real-file.png'"
+    )
+    assert_equal(expected_message, str(error))
+
+
+@istest
+def error_is_raised_if_file_uri_cannot_be_opened():
+    files = Files("/tmp")
+    error = assert_raises(InvalidFileReferenceError, lambda: files.open("file:///not-a-real-file.png"))
+    expected_message = "could not open external image: 'file:///not-a-real-file.png' (document directory: '/tmp')\n"
+    assert str(error).startswith(expected_message)
diff --git a/tests/mammoth_tests.py b/tests/mammoth_tests.py
index f29ae0f..906f49b 100644
--- a/tests/mammoth_tests.py
+++ b/tests/mammoth_tests.py
@@ -96,7 +96,7 @@ def warn_if_images_stored_outside_of_document_are_not_found():
         with open(document_path, "rb") as fileobj:
             result = mammoth.convert_to_html(fileobj=fileobj)
             assert_equal("", result.value)
-            expected_warning = "could not open external image 'tiny-picture.png' from document directory '{0}'\n[Errno 2] No such file or directory".format(temp_dir.path)
+            expected_warning = "could not open external image: 'tiny-picture.png'"
             assert_equal("warning", result.messages[0].type)
             assert result.messages[0].message.startswith(expected_warning), "message was: " + result.messages[0].message
             assert_equal(1, len(result.messages))
diff --git a/tests/testing.py b/tests/testing.py
index d70ded6..c5013dc 100644
--- a/tests/testing.py
+++ b/tests/testing.py
@@ -7,3 +7,12 @@ from nose.tools import nottest
 def test_path(path):
     this_dir = os.path.dirname(__file__)
     return os.path.join(this_dir, "test-data", path)
+
+
+def assert_raises(exception, func):
+    try:
+        func()
+        assert False, "Expected " + exception.__name__
+    except exception as error:
+        return error
+