py3: suppress the output of open() using `and None`

This patch suppresses the output of open() on Python 3 as it does not return any
output on Python 2.

This makes test-diffstat.t pass on Python 3.5

Differential Revision: https://phab.mercurial-scm.org/D3128

tests/test-diffstat.t

@@ -1,238 +1,238 b''
   $ hg init repo
   $ cd repo
   $ i=0; while [ "$i" -lt 213 ]; do echo a >> a; i=`expr $i + 1`; done
   $ hg add a
   $ cp a b
   $ hg add b
 
 Wide diffstat:
 
   $ hg diff --stat
    a |  213 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    b |  213 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 426 insertions(+), 0 deletions(-)
 
 diffstat width:
 
   $ COLUMNS=24 hg diff --config ui.interactive=true --stat
    a |  213 ++++++++++++++
    b |  213 ++++++++++++++
    2 files changed, 426 insertions(+), 0 deletions(-)
 
   $ hg ci -m adda
 
   $ cat >> a <<EOF
   > a
   > a
   > a
   > EOF
 
 Narrow diffstat:
 
   $ hg diff --stat
    a |  3 +++
    1 files changed, 3 insertions(+), 0 deletions(-)
 
   $ hg ci -m appenda
 
-  >>> open("c", "wb").write(b"\0")
+  >>> open("c", "wb").write(b"\0") and None
   $ touch d
   $ hg add c d
 
 Binary diffstat:
 
   $ hg diff --stat
    c |  Bin 
    1 files changed, 0 insertions(+), 0 deletions(-)
 
 Binary git diffstat:
 
   $ hg diff --stat --git
    c |  Bin 
    d |    0 
    2 files changed, 0 insertions(+), 0 deletions(-)
 
   $ hg ci -m createb
 
-  >>> open("file with spaces", "wb").write(b"\0")
+  >>> open("file with spaces", "wb").write(b"\0") and None
   $ hg add "file with spaces"
 
 Filename with spaces diffstat:
 
   $ hg diff --stat
    file with spaces |  Bin 
    1 files changed, 0 insertions(+), 0 deletions(-)
 
 Filename with spaces git diffstat:
 
   $ hg diff --stat --git
    file with spaces |  Bin 
    1 files changed, 0 insertions(+), 0 deletions(-)
 
 Filename without "a/" or "b/" (issue5759):
 
   $ hg diff --config 'diff.noprefix=1' -c1 --stat --git
    a |  3 +++
    1 files changed, 3 insertions(+), 0 deletions(-)
   $ hg diff --config 'diff.noprefix=1' -c2 --stat --git
    c |  Bin 
    d |    0 
    2 files changed, 0 insertions(+), 0 deletions(-)
 
   $ hg log --config 'diff.noprefix=1' -r '1:' -p --stat --git
   changeset:   1:3a95b07bb77f
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     appenda
   
    a |  3 +++
    1 files changed, 3 insertions(+), 0 deletions(-)
   
   diff --git a a
   --- a
   +++ a
   @@ -211,3 +211,6 @@
    a
    a
    a
   +a
   +a
   +a
   
   changeset:   2:c60a6c753773
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     createb
   
    c |  Bin 
    d |    0 
    2 files changed, 0 insertions(+), 0 deletions(-)
   
   diff --git c c
   new file mode 100644
   index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..f76dd238ade08917e6712764a16a22005a50573d
   GIT binary patch
   literal 1
   Ic${MZ000310RR91
   
   diff --git d d
   new file mode 100644
   
 
 diffstat within directories:
 
   $ hg rm -f 'file with spaces'
 
   $ mkdir dir1 dir2
   $ echo new1 > dir1/new
   $ echo new2 > dir2/new
   $ hg add dir1/new dir2/new
   $ hg diff --stat
    dir1/new |  1 +
    dir2/new |  1 +
    2 files changed, 2 insertions(+), 0 deletions(-)
 
   $ hg diff --stat --root dir1
    new |  1 +
    1 files changed, 1 insertions(+), 0 deletions(-)
 
   $ hg diff --stat --root dir1 dir2
   warning: dir2 not inside relative root dir1
 
   $ hg diff --stat --root dir1 -I dir1/old
 
   $ cd dir1
   $ hg diff --stat .
    dir1/new |  1 +
    1 files changed, 1 insertions(+), 0 deletions(-)
   $ hg diff --stat --root .
    new |  1 +
    1 files changed, 1 insertions(+), 0 deletions(-)
 
   $ hg diff --stat --root ../dir1 ../dir2
   warning: ../dir2 not inside relative root .
 
   $ hg diff --stat --root . -I old
 
   $ cd ..
 
 Files with lines beginning with '--' or '++' should be properly counted in diffstat
 
   $ hg up -Cr tip
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ rm dir1/new
   $ rm dir2/new
   $ rm "file with spaces"
   $ cat > file << EOF
   > line 1
   > line 2
   > line 3
   > EOF
   $ hg commit -Am file
   adding file
 
 Lines added starting with '--' should count as additions
   $ cat > file << EOF
   > line 1
   > -- line 2, with dashes
   > line 3
   > EOF
 
   $ hg diff --root .
   diff -r be1569354b24 file
   --- a/file	Thu Jan 01 00:00:00 1970 +0000
   +++ b/file	* (glob)
   @@ -1,3 +1,3 @@
    line 1
   -line 2
   +-- line 2, with dashes
    line 3
 
   $ hg diff --root . --stat
    file |  2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)
 
 Lines changed starting with '--' should count as deletions
   $ hg commit -m filev2
   $ cat > file << EOF
   > line 1
   > -- line 2, with dashes, changed again
   > line 3
   > EOF
 
   $ hg diff --root .
   diff -r 160f7c034df6 file
   --- a/file	Thu Jan 01 00:00:00 1970 +0000
   +++ b/file	* (glob)
   @@ -1,3 +1,3 @@
    line 1
   --- line 2, with dashes
   +-- line 2, with dashes, changed again
    line 3
 
   $ hg diff --root . --stat
    file |  2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)
 
 Lines changed starting with '--' should count as deletions
 and starting with '++' should count as additions
   $ cat > file << EOF
   > line 1
   > ++ line 2, switched dashes to plusses
   > line 3
   > EOF
 
   $ hg diff --root .
   diff -r 160f7c034df6 file
   --- a/file	Thu Jan 01 00:00:00 1970 +0000
   +++ b/file	* (glob)
   @@ -1,3 +1,3 @@
    line 1
   --- line 2, with dashes
   +++ line 2, switched dashes to plusses
    line 3
 
   $ hg diff --root . --stat
    file |  2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)