[PATCH 1 of 4 v4] hghave: make bzr checks stricter

[timeless]

# HG changeset patch
# User timeless <timeless at mozdev.org>
# Date 1472165499 0
#      Thu Aug 25 22:51:39 2016 +0000
# Node ID 2b368e1f8ac00774b2a1d24c6cf9282e3cd24f1a
# Parent  b1809f5d7630a3fff0fa715bbd30dba0f07672a8
# Available At https://bitbucket.org/timeless/mercurial-crew
#              hg pull https://bitbucket.org/timeless/mercurial-crew -r 2b368e1f8ac0
hghave: make bzr checks stricter

My bzr does not have bzrlib.revisionspec.RevisionSpec,
and thus tests were failing because convert refused to believe in bzr,
but hghave without this change thought it was available.

diff -r b1809f5d7630 -r 2b368e1f8ac0 tests/hghave.py
--- a/tests/hghave.py	Mon Aug 15 20:39:33 2016 -0700
+++ b/tests/hghave.py	Thu Aug 25 22:51:39 2016 +0000
@@ -110,6 +110,10 @@
 def has_bzr():
     try:
         import bzrlib
+        import bzrlib.bzrdir
+        import bzrlib.errors
+        import bzrlib.revision
+        import bzrlib.revisionspec.RevisionSpec
         return bzrlib.__doc__ is not None
     except ImportError:
         return False