tests: enable debugruntest for test-pager.t

Summary:
This test wasn't using `debugruntest` since it's one of those tests that shells out to Python for various things.

Making this work on Windows required a couple of changes, as non-debugruntest tests rely on having bash and bash-like utils for running:
- The test had to shell out and used the `echo` command for this. On Bash using `echo` is fine, but on Windows cmd's echo does not output a new line
- Like in D54347528, `$PYTHON` could no longer be used on things hg called
- Since the test was essentially running on Bash, the Python scripts this test was shelling out to could no longer use `sys.stdout.write`.
  - As this test was previously running essentially on Bash, the newlines from `sys.stdout.write` contained carriage returns
  - This was changed to use `hg dbsh` and `ui.write` instead

Reviewed By: muirdm

Differential Revision: D54826008

fbshipit-source-id: 16460ddd30dd8dc8a27ca66580ada8f50b774905

eden/scm/tests/test-pager.t

@@ -1,21 +1,24 @@
+#debugruntest-compatible
+#inprocess-hg-incompatible
+
   $ eagerepo
   $ setconfig devel.segmented-changelog-rev-compat=true
   $ cat >> fakepager.py <<EOF
   > import sys
   > printed = False
   > for line in sys.stdin:
-  >     sys.stdout.write('paged! %r\n' % line)
+  >     ui.write('paged! %r\n' % line)
   >     printed = True
   > if not printed:
-  >     sys.stdout.write('paged empty output!\n')
+  >     ui.write('paged empty output!\n')
   > EOF
 
 Enable ui.assume-tty so that the pager will start, and set the pager to our
 fake pager that lets us see when the pager was running.
   $ setconfig ui.assume-tty=yes ui.color=no
   $ cat >>$HGRCPATH <<EOF
   > [pager]
-  > pager = $PYTHON $TESTTMP/fakepager.py
+  > pager = hg dbsh $TESTTMP/fakepager.py
   > EOF
 
   $ hg init repo
@@ -212,10 +215,19 @@ improve this.
 
 Pager works with shell aliases.
 
+#if windows
+On Windows cmd's echo is used, which prints carriage returns, so we use hg instead
+
+  $ cat >> $HGRCPATH <<EOF
+  > [alias]
+  > echoa = !hg dbsh -c "ui.write('a\n')"
+  > EOF
+#else
   $ cat >> $HGRCPATH <<EOF
   > [alias]
   > echoa = !echo a
   > EOF
+#endif
 
   $ hg echoa
   a
@@ -343,13 +355,11 @@ During pushbuffer, pager should not start:
 
 Environment variables like LESS and LV are set automatically:
   $ cat > $TESTTMP/printlesslv.py <<EOF
-  > from __future__ import absolute_import
   > import os
   > import sys
   > sys.stdin.read()
   > for name in ['LESS', 'LV']:
-  >     sys.stdout.write(('%s=%s\n') % (name, os.environ.get(name, '-')))
-  > sys.stdout.flush()
+  >     ui.write(('%s=%s\n') % (name, os.environ.get(name, '-')))
   > EOF
 
   $ cat >> $HGRCPATH <<EOF
@@ -358,7 +368,7 @@ Environment variables like LESS and LV are set automatically:
   > [ui]
   > formatted=1
   > [pager]
-  > pager = $PYTHON $TESTTMP/printlesslv.py
+  > pager = hg dbsh $TESTTMP/printlesslv.py
   > EOF
   $ unset LESS
   $ unset LV