Store repository on window manager so it isn't saved in the .blend

We store it outside blender in JSON anyway, storing it two places at
once could be confusing. We can move it back into the .blend later if it
seems that would be preferred.

bpkg/subproc.py

@@ -310,10 +310,7 @@ class Repository:
         """
         Read repository from a json file at `path`.
         """
-        try:
-            repo_file = path.open('r', encoding='utf-8')
-        except IOError as err:
-            raise BadRepository from err
+        repo_file = path.open('r', encoding='utf-8')
 
         with repo_file:
             try:
@@ -513,14 +510,12 @@ def refresh(pipe_to_blender, storage_path: pathlib.Path, repository_url: str):
     log = logging.getLogger(__name__ + '.refresh')
 
     repo_path = storage_path / 'repo.json'
-    try:
+    if repo_path.exists():
         repo = Repository.from_file(repo_path)
-    except BadRepository as err:
-        log.warning("Failed to read existing repository: %s. Continuing download.", err)
-        repo = Repository(repository_url)
-
-    if repo.url != repository_url:
-        # We're getting a new repository
+        if repo.url != repository_url:
+            # We're getting a new repository
+            repo = Repository(repository_url)
+    else:
         repo = Repository(repository_url)
 
     try: