fix: Add gives proper error message when library.toml missing

Added also a small helpful message about how to create a library.toml

fixes #3

src/filesystem_operations/libraryreader.py

@@ -2,4 +2,10 @@
 
 
 def load_library(filename):
-    return tomli.load(open(filename, "rb"))
+    try:
+        return tomli.load(open(filename, "rb"))
+    except(FileNotFoundError):
+        raise LibraryFileMissing
+
+class LibraryFileMissing(Exception):
+    pass

src/gallerycmd/add/add.py

@@ -1,4 +1,5 @@
 import sys
+from filesystem_operations.libraryreader import LibraryFileMissing
 from filesystem_operations.librarysaver import save_library
 
 from gallerycmd.parser import subparsers
@@ -15,6 +16,10 @@ def main(args):
     except(FileNotFoundError):
         print("No such image:", args.filename)
         exit(1)
+    except(LibraryFileMissing):
+        print("\nNo library.toml present!\n")
+        print("  You can create a new gallery by issuing 'gallery init > library.toml'")
+        exit(1)
 
 
 def add_image(filename, title="", description="", tags=[]):

test/integration/filesystem_operations/test_libraryreader.py

@@ -1,15 +1,15 @@
 import pytest
 import tomli
 
-from filesystem_operations.libraryreader import load_library
+from filesystem_operations.libraryreader import LibraryFileMissing, load_library
 
 
 def test_load_gallery_fails_without_filename():
     with pytest.raises(TypeError, match="missing 1 required positional argument"):
         load_library()
 
 def test_file_not_found(tmp_path):
-    with pytest.raises(FileNotFoundError):
+    with pytest.raises(LibraryFileMissing):
         load_library(tmp_path / "foo")
 
 def test_file_not_toml(tmp_path):

test/integration/imagegallery/test_imagegallery.py

@@ -1,12 +1,13 @@
 import pytest
 from _pytest import monkeypatch
+from filesystem_operations.libraryreader import LibraryFileMissing
 
 from test.integration.filesystem_helpers import mkdir
 from Imagegallery import Filetree, LibraryToml, Imagegallery
 
 def test_throws_if_no_library_toml(tmp_path, monkeypatch):
     monkeypatch.chdir(tmp_path)
-    with pytest.raises(FileNotFoundError):
+    with pytest.raises(LibraryFileMissing):
         gallery = Imagegallery.from_disk()
 
 def test_works_if_file_present(environment):