tests: update test-merge-symlinks to pass our import checker

tests/test-merge-symlinks.t

@@ -1,64 +1,65 b''
   $ cat > echo.py <<EOF
   > #!$PYTHON
-  > from __future__ import print_function
-  > import os, sys
+  > from __future__ import absolute_import, print_function
+  > import os
+  > import sys
   > try:
   >     import msvcrt
   >     msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
   >     msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
   > except ImportError:
   >     pass
   > 
   > for k in ('HG_FILE', 'HG_MY_ISLINK', 'HG_OTHER_ISLINK', 'HG_BASE_ISLINK'):
   >     print(k, os.environ[k])
   > EOF
 
 Create 2 heads containing the same file, once as
 a file, once as a link. Bundle was generated with:
 
 # hg init t
 # cd t
 # echo a > a
 # hg ci -qAm t0 -d '0 0'
 # echo l > l
 # hg ci -qAm t1 -d '1 0'
 # hg up -C 0
 # ln -s a l
 # hg ci -qAm t2 -d '2 0'
 # echo l2 > l2
 # hg ci -qAm t3 -d '3 0'
 
   $ hg init t
   $ cd t
   $ hg -q pull "$TESTDIR/bundles/test-merge-symlinks.hg"
   $ hg up -C 3
   3 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
 Merge them and display *_ISLINK vars
 merge heads
 
   $ hg merge --tool="$PYTHON ../echo.py"
   merging l
   HG_FILE l
   HG_MY_ISLINK 1
   HG_OTHER_ISLINK 0
   HG_BASE_ISLINK 0
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
 
 Test working directory symlink bit calculation wrt copies,
 especially on non-supporting systems.
 merge working directory
 
   $ hg up -C 2
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ hg copy l l2
   $ HGMERGE="$PYTHON ../echo.py" hg up 3
   merging l2
   HG_FILE l2
   HG_MY_ISLINK 1
   HG_OTHER_ISLINK 0
   HG_BASE_ISLINK 0
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
 
   $ cd ..