convert: bail out in Subversion source if encountering non-ASCII HTTP(S) URL Before this patch, in the tested case, urllib raised `httplib.InvalidURL: URL can't contain control characters. '/\xff/!svn/ver/0/.svn' (found at least '\xff')`, which resulted in that the URL was never recognized as a Subversion repository. This patch adds a check that bails out if the URL contains non-ASCII characters. The warning is not overly user-friendly, but giving the user something to type into a search engine is definitively better than not explaining why the repository was not recognized. We could support non-ASCII chracters by quoting them before passing them to urllib. However, we would want to be compatible with what the `svn` command does, which converts the URL from the locale encoding to UTF-8, percent-encodes it and sends it to the server. If the locale encoding is not UTF-8, the behavior is IMHO not very intuitive, as the `svn` command may send different (percent-encoded) octets than what was passed on the console. Instead of copying this behavior, we better leave it forbidden.

--- a/tests/test-convert-svn-encoding.t	Mon Jun 29 02:05:12 2020 +0200
+++ b/tests/test-convert-svn-encoding.t	Tue Jun 30 04:55:52 2020 +0200
@@ -153,6 +153,16 @@
 
   $ cd ..
 
+Subversion sources don't support non-ASCII characters in HTTP(S) URLs.
+
+  $ XFF=$($PYTHON -c 'from mercurial.utils.procutil import stdout; stdout.write(b"\xff")')
+  $ hg convert --source-type=svn http://localhost:$HGPORT/$XFF test
+  initializing destination test repository
+  Subversion sources don't support non-ASCII characters in HTTP(S) URLs. Please percent-encode them.
+  http://localhost:$HGPORT/\xff does not look like a Subversion repository (esc)
+  abort: http://localhost:$HGPORT/\xff: missing or unsupported repository (esc)
+  [255]
+
 #if py3
 For now, on Python 3, we abort when encountering non-UTF-8 percent-encoded
 bytes in a filename.