tests: fix Python3 issues in Python one-liners in test-patchbomb.t

# skip-blame just byte prefixes

Differential Revision: https://phab.mercurial-scm.org/D4220

tests/test-patchbomb.t

@@ -442,7 +442,7 b' with a specific bundle type'
   --===============*==-- (glob)
 
 utf-8 patch:
-  $ $PYTHON -c 'fp = open("utf", "wb"); fp.write("h\xC3\xB6mma!\n"); fp.close();'
+  $ $PYTHON -c 'fp = open("utf", "wb"); fp.write(b"h\xC3\xB6mma!\n"); fp.close();'
   $ hg commit -A -d '4 0' -m 'utf-8 content'
   adding description
   adding utf
@@ -551,7 +551,7 b' mime encoded mbox (base64):'
   $ rm mbox
 
 mime encoded mbox (quoted-printable):
-  $ $PYTHON -c 'fp = open("long", "wb"); fp.write("%s\nfoo\n\nbar\n" % ("x" * 1024)); fp.close();'
+  $ $PYTHON -c 'fp = open("long", "wb"); fp.write(b"%s\nfoo\n\nbar\n" % ("x" * 1024)); fp.close();'
   $ hg commit -A -d '4 0' -m 'long line'
   adding long
 
@@ -665,7 +665,7 b' mime encoded mbox (quoted-printable):'
   $ rm mbox
 
 iso-8859-1 patch:
-  $ $PYTHON -c 'fp = open("isolatin", "wb"); fp.write("h\xF6mma!\n"); fp.close();'
+  $ $PYTHON -c 'fp = open("isolatin", "wb"); fp.write(b"h\xF6mma!\n"); fp.close();'
   $ hg commit -A -d '5 0' -m 'isolatin 8-bit encoding'
   adding isolatin