test: replace a many occurence of `python` with `$PYTHON`

test: replace a many occurence of `python` with `$PYTHON`

Otherwise this can use the wrong python version, or worse, not find any python
at all.

Differential Revision: https://phab.mercurial-scm.org/D9730

--- a/tests/library-infinitepush.sh	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/library-infinitepush.sh	Tue Jan 12 22:43:55 2021 +0100
@@ -15,7 +15,7 @@
 [extensions]
 infinitepush=
 [ui]
-ssh = python "$TESTDIR/dummyssh"
+ssh = $PYTHON "$TESTDIR/dummyssh"
 [infinitepush]
 branchpattern=re:scratch/.*
 EOF

--- a/tests/remotefilelog-library.sh	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/remotefilelog-library.sh	Tue Jan 12 22:43:55 2021 +0100
@@ -8,7 +8,7 @@
 rebase=
 strip=
 [ui]
-ssh=python "$TESTDIR/dummyssh"
+ssh=$PYTHON "$TESTDIR/dummyssh"
 [server]
 preferuncompressed=True
 [experimental]

--- a/tests/test-demandimport.py	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/test-demandimport.py	Tue Jan 12 22:43:55 2021 +0100
@@ -14,7 +14,7 @@
 
 # Only run if demandimport is allowed
 if subprocess.call(
-    ['python', '%s/hghave' % os.environ['TESTDIR'], 'demandimport']
+    [os.environ['PYTHON'], '%s/hghave' % os.environ['TESTDIR'], 'demandimport']
 ):
     sys.exit(80)
 

--- a/tests/test-infinitepush-ci.t	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/test-infinitepush-ci.t	Tue Jan 12 22:43:55 2021 +0100
@@ -10,7 +10,7 @@
   $ . "$TESTDIR/library-infinitepush.sh"
   $ cat >> $HGRCPATH <<EOF
   > [ui]
-  > ssh = python "$TESTDIR/dummyssh"
+  > ssh = $PYTHON "$TESTDIR/dummyssh"
   > [alias]
   > glog = log -GT "{rev}:{node|short} {desc}\n{phase}"
   > EOF

--- a/tests/test-nointerrupt.t	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/test-nointerrupt.t	Tue Jan 12 22:43:55 2021 +0100
@@ -59,7 +59,7 @@
   > EOF
 
 Test ctrl-c
-  $ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
+  $ $PYTHON $TESTTMP/timeout.py -s INT 1 hg sleep 2
   interrupted!
   [124]
 
@@ -68,7 +68,7 @@
   > nointerrupt = yes
   > EOF
 
-  $ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
+  $ $PYTHON $TESTTMP/timeout.py -s INT 1 hg sleep 2
   interrupted!
   [124]
 
@@ -77,7 +77,7 @@
   > nointerrupt-interactiveonly = False
   > EOF
 
-  $ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
+  $ $PYTHON $TESTTMP/timeout.py -s INT 1 hg sleep 2
   shutting down cleanly
   press ^C again to terminate immediately (dangerous)
   end of unsafe operation

--- a/tests/test-remotefilelog-cacheprocess.t	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/test-remotefilelog-cacheprocess.t	Tue Jan 12 22:43:55 2021 +0100
@@ -66,7 +66,7 @@
 
   $ cat >> $HGRCPATH <<EOF
   > [remotefilelog]
-  > cacheprocess = python $TESTTMP/cacheprocess-logger.py
+  > cacheprocess = $PYTHON $TESTTMP/cacheprocess-logger.py
   > EOF
 
 Test cache keys and cache misses.

--- a/tests/test-update-atomic.t	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/test-update-atomic.t	Tue Jan 12 22:43:55 2021 +0100
@@ -54,7 +54,7 @@
   $ hg update -r 1 --config extensions.showwrites=.hg/showwrites.py 2>&1 | grep "a1'.*wb"
   ('vfs open', ('a1', 'wb'), [('atomictemp', False), ('backgroundclose', True)])
 
-  $ python $TESTTMP/show_mode.py *
+  $ $PYTHON $TESTTMP/show_mode.py *
   a1:0644
   a2:0755
   b1:0644
@@ -76,7 +76,7 @@
   $ hg update -r 1
   6 files updated, 0 files merged, 1 files removed, 0 files unresolved
 
-  $ python $TESTTMP/show_mode.py *
+  $ $PYTHON $TESTTMP/show_mode.py *
   a1:0644
   a2:0755
   b1:0644
@@ -88,7 +88,7 @@
 
   $ chmod a-w ro
 
-  $ python $TESTTMP/show_mode.py ro
+  $ $PYTHON $TESTTMP/show_mode.py ro
   ro:0444
 
 Now the file is present, try to update and check the permissions of the file
@@ -96,7 +96,7 @@
   $ hg up -r 2
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
-  $ python $TESTTMP/show_mode.py ro
+  $ $PYTHON $TESTTMP/show_mode.py ro
   ro:0644
 
 # The file which was read-only is now writable in the default behavior
@@ -121,7 +121,7 @@
   C ro
 
 Check the file permission after update
-  $ python $TESTTMP/show_mode.py *
+  $ $PYTHON $TESTTMP/show_mode.py *
   a1:0644
   a2:0755
   b1:0644
@@ -133,7 +133,7 @@
 
   $ chmod a-w ro
 
-  $ python $TESTTMP/show_mode.py ro
+  $ $PYTHON $TESTTMP/show_mode.py ro
   ro:0444
 
 Now the file is present, try to update and check the permissions of the file
@@ -141,7 +141,7 @@
   $ hg update -r 2 --traceback
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
-  $ python $TESTTMP/show_mode.py ro
+  $ $PYTHON $TESTTMP/show_mode.py ro
   ro:0644
 
 # The behavior is the same as without atomic update

--- a/tests/test-verify-repo-operations.py	Tue Jan 12 17:32:08 2021 -0800
+++ b/tests/test-verify-repo-operations.py	Tue Jan 12 22:43:55 2021 +0100
@@ -11,7 +11,9 @@
 import sys
 
 # Only run if slow tests are allowed
-if subprocess.call(['python', '%s/hghave' % os.environ['TESTDIR'], 'slow']):
+if subprocess.call(
+    [os.environ['PYTHON'], '%s/hghave' % os.environ['TESTDIR'], 'slow']
+):
     sys.exit(80)
 
 # These tests require Hypothesis and pytz to be installed.
@@ -352,7 +354,7 @@
             o.write(content)
         self.log.append(
             (
-                "$ python -c 'import binascii; "
+                "$ $PYTHON -c 'import binascii; "
                 "print(binascii.unhexlify(\"%s\"))' > %s"
             )
             % (