Initial multiple repository support

And lots of code reshuffling which likely should've been done in
separate commits..

package_manager/bpkg/utils.py

@@ -4,6 +4,18 @@ import shutil
 import logging
 
 
+def format_filename(s: str, ext=None) -> str:
+    """Take a string and turn it into a reasonable filename"""
+    import string
+    if ext is None:
+        ext = ""
+    valid_chars = "-_.() %s%s" % (string.ascii_letters, string.digits)
+    filename = ''.join(char for char in s if char in valid_chars)
+    filename = filename.replace(' ','_')
+    filename.lower()
+    filename += ext
+    return filename
+
 def download(url: str, destination: Path, progress_callback=None) -> Path:
     """
     Downloads file at the given url, and if progress_callback is specified,
@@ -17,12 +29,11 @@ def download(url: str, destination: Path, progress_callback=None) -> Path:
     log = logging.getLogger('%s.download' % __name__)
 
     if progress_callback is None:
-        # assing to do nothing function
+        # assign to do-nothing function
         progress_callback = lambda x: None
 
     progress_callback(0)
 
-
     # derive filename from url if `destination` is an existing directory, otherwise use `destination` directly
     if destination.is_dir():
         # TODO: get filename from Content-Disposition header, if available.
@@ -35,10 +46,10 @@ def download(url: str, destination: Path, progress_callback=None) -> Path:
 
     log.info('Downloading %s -> %s', url, local_fpath)
 
-    try:
-        resp = requests.get(url, stream=True, verify=True)
-    except requests.exceptions.RequestException as err:
-        raise exceptions.DownloadException(err) from err
+    # try:
+    resp = requests.get(url, stream=True, verify=True)
+    # except requests.exceptions.RequestException as err:
+    #     raise exceptions.DownloadException(err) from err
 
     try:
         resp.raise_for_status()
@@ -187,3 +198,21 @@ def install(src_file: Path, dest_dir: Path):
             raise exceptions.InstallException("Failed to copy file to '%s': %s" % (dest_dir, err)) from err
 
     log.debug("Installation succeeded")
+
+
+# def load_repository(repo_storage_path: Path, repo_name: str) -> Repository:
+#     """Loads <repo_name>.json from <repo_storage_path>"""
+#     pass
+#
+# def download_repository(repo_storage_path: Path, repo_name: str):
+#     """Loads <repo_name>.json from <repo_storage_path>"""
+#     pass
+# this is done in Repository
+
+
+def add_repojson_to_url(url: str) -> str:
+    """Add `repo.json` to the path component of a url"""
+    from urllib.parse import urlsplit, urlunsplit
+    parsed_url = urlsplit(url)
+    new_path = parsed_url.path + "/repo.json"
+    return urlunsplit((parsed_url.scheme, parsed_url.netloc, new_path, parsed_url.query, parsed_url.fragment))