tests: conditionalize test output on Python 3.7

Python 3.7 changed behavior of urllib.parse.quote() from RFC 2396
to RFC 3986 and ~ is now in the set of reserved characters and
isn't escaped.

We conditioanlize test output accordingly.

Differential Revision: https://phab.mercurial-scm.org/D5717

tests/test-static-http.t

@@ -227,9 +227,11 b' List of files accessed over HTTP:'
   /.hg/requires
   /.hg/store/00changelog.i
   /.hg/store/00manifest.i
-  /.hg/store/data/%7E2ehgsub.i
-  /.hg/store/data/%7E2ehgsubstate.i
+  /.hg/store/data/%7E2ehgsub.i (no-py37 !)
+  /.hg/store/data/%7E2ehgsubstate.i (no-py37 !)
   /.hg/store/data/a.i
+  /.hg/store/data/~2ehgsub.i (py37 !)
+  /.hg/store/data/~2ehgsubstate.i (py37 !)
   /notarepo/.hg/00changelog.i
   /notarepo/.hg/requires
   /remote-with-names/.hg/bookmarks
@@ -243,8 +245,9 b' List of files accessed over HTTP:'
   /remote-with-names/.hg/requires
   /remote-with-names/.hg/store/00changelog.i
   /remote-with-names/.hg/store/00manifest.i
-  /remote-with-names/.hg/store/data/%7E2ehgtags.i
+  /remote-with-names/.hg/store/data/%7E2ehgtags.i (no-py37 !)
   /remote-with-names/.hg/store/data/foo.i
+  /remote-with-names/.hg/store/data/~2ehgtags.i (py37 !)
   /remote/.hg/bookmarks
   /remote/.hg/bookmarks.current
   /remote/.hg/cache/branch2-base
@@ -258,10 +261,12 b' List of files accessed over HTTP:'
   /remote/.hg/requires
   /remote/.hg/store/00changelog.i
   /remote/.hg/store/00manifest.i
-  /remote/.hg/store/data/%7E2edotfile%20with%20spaces.i
-  /remote/.hg/store/data/%7E2ehgtags.i
+  /remote/.hg/store/data/%7E2edotfile%20with%20spaces.i (no-py37 !)
+  /remote/.hg/store/data/%7E2ehgtags.i (no-py37 !)
   /remote/.hg/store/data/bar.i
   /remote/.hg/store/data/quux.i
+  /remote/.hg/store/data/~2edotfile%20with%20spaces.i (py37 !)
+  /remote/.hg/store/data/~2ehgtags.i (py37 !)
   /remotempty/.hg/bookmarks
   /remotempty/.hg/bookmarks.current
   /remotempty/.hg/requires
@@ -275,5 +280,6 b' List of files accessed over HTTP:'
   /sub/.hg/requires
   /sub/.hg/store/00changelog.i
   /sub/.hg/store/00manifest.i
-  /sub/.hg/store/data/%7E2ehgtags.i
+  /sub/.hg/store/data/%7E2ehgtags.i (no-py37 !)
   /sub/.hg/store/data/test.i
+  /sub/.hg/store/data/~2ehgtags.i (py37 !)