patch 8.2.0665: wrongly assuming Python executable is called "python"

Problem:    Wrongly assuming Python executable is called "python".
Solution:   Use detected python command. (Ken Takata, closes #6016)
            Also use CheckFunction if possible.

src/testdir/check.vim

@@ -52,6 +52,14 @@ func CheckExecutable(name)
   endif
 endfunc
 
+" Command to check for the presence of python.  Argument should have been
+" obtained with PythonProg()
+func CheckPython(name)
+  if a:name == ''
+    throw 'Skipped: python command not available'
+  endif
+endfunc
+
 " Command to check for running on MS-Windows
 command CheckMSWindows call CheckMSWindows()
 func CheckMSWindows()

src/testdir/test_terminal.vim

@@ -715,10 +715,10 @@ func Test_terminal_write_stdin()
 endfunc
 
 func Test_terminal_eof_arg()
-  CheckExecutable python
+  call CheckPython(s:python)
 
   call setline(1, ['print("hello")'])
-  1term ++eof=exit(123) python
+  exe '1term ++eof=exit(123) ' .. s:python
   " MS-Windows echoes the input, Unix doesn't.
   if has('win32')
     call WaitFor({-> getline('$') =~ 'exit(123)'})
@@ -733,22 +733,22 @@ endfunc
 
 func Test_terminal_eof_arg_win32_ctrl_z()
   CheckMSWindows
-  CheckExecutable python
+  call CheckPython(s:python)
 
   call setline(1, ['print("hello")'])
-  1term ++eof=<C-Z> python
+  exe '1term ++eof=<C-Z> ' .. s:python
   call WaitForAssert({-> assert_match('\^Z', getline(line('$') - 1))})
   call assert_match('\^Z', getline(line('$') - 1))
   %bwipe!
 endfunc
 
 func Test_terminal_duplicate_eof_arg()
-  CheckExecutable python
+  call CheckPython(s:python)
 
   " Check the last specified ++eof arg is used and should not memory leak.
   new
   call setline(1, ['print("hello")'])
-  1term ++eof=<C-Z> ++eof=exit(123) python
+  exe '1term ++eof=<C-Z> ++eof=exit(123) ' .. s:python
   " MS-Windows echoes the input, Unix doesn't.
   if has('win32')
     call WaitFor({-> getline('$') =~ 'exit(123)'})
@@ -1571,9 +1571,8 @@ func Test_terminal_api_call_fail_delete()
 endfunc
 
 func Test_terminal_ansicolors_default()
-  if !exists('*term_getansicolors')
-    throw 'Skipped: term_getansicolors() not supported'
-  endif
+  CheckFunction term_getansicolors
+
   let colors = [
 	\ '#000000', '#e00000',
 	\ '#00e000', '#e0e000',
@@ -1606,9 +1605,8 @@ let s:test_colors = [
 
 func Test_terminal_ansicolors_global()
   CheckFeature termguicolors
-  if !exists('*term_getansicolors')
-    throw 'Skipped: term_getansicolors() not supported'
-  endif
+  CheckFunction term_getansicolors
+
   let g:terminal_ansi_colors = reverse(copy(s:test_colors))
   let buf = Run_shell_in_terminal({})
   call assert_equal(g:terminal_ansi_colors, term_getansicolors(buf))
@@ -1621,9 +1619,8 @@ endfunc
 
 func Test_terminal_ansicolors_func()
   CheckFeature termguicolors
-  if !exists('*term_getansicolors')
-    throw 'Skipped: term_getansicolors() not supported'
-  endif
+  CheckFunction term_getansicolors
+
   let g:terminal_ansi_colors = reverse(copy(s:test_colors))
   let buf = Run_shell_in_terminal({'ansi_colors': s:test_colors})
   call assert_equal(s:test_colors, term_getansicolors(buf))
@@ -2588,6 +2585,7 @@ func Test_hidden_terminal()
 endfunc
 
 func Test_term_nasty_callback()
+  CheckExecutable sh
   func OpenTerms()
     set hidden
     let g:buf0 = term_start('sh', #{hidden: 1})

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    665,
 /**/
     664,
 /**/