pmb.helpers.git: Use NonBugError for get_upstream_remote

This is a problem in the pmaports.git state, not a bug in pmbootstrap.

pmb/helpers/git.py

@@ -13,6 +13,7 @@ import pmb.chroot.apk
 import pmb.config
 import pmb.helpers.pmaports
 import pmb.helpers.run
+from pmb.helpers.exceptions import NonBugError
 from pmb.meta import Cache
 
 re_branch_aports = re.compile(r"^\d+\.\d\d+-stable$")
@@ -105,7 +106,7 @@ def get_upstream_remote(aports: Path):
     for line in output.split("\n"):
         if any(u in line for u in urls):
             return line.split("\t", 1)[0]
-    raise RuntimeError(
+    raise NonBugError(
         f"{name_repo}: could not find remote name for any URL '{urls}' in git"
         f" repository: {aports}"
     )