patch 8.0.0251: not easy to select Python 2 or 3

Problem:    It is not so easy to write a script that works with both Python 2
            and Python 3, even when the Python code works with both.
Solution:   Add 'pyxversion', :pyx, etc. (Marc Weber, Ken Takata)
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index c3db6fe..12abb78 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -176,6 +176,8 @@
 	    test_packadd.res \
 	    test_perl.res \
 	    test_profile.res \
+	    test_pyx2.res \
+	    test_pyx3.res \
 	    test_quickfix.res \
 	    test_retab.res \
 	    test_ruby.res \
diff --git a/src/testdir/pyxfile/py2_magic.py b/src/testdir/pyxfile/py2_magic.py
new file mode 100644
index 0000000..819892f
--- /dev/null
+++ b/src/testdir/pyxfile/py2_magic.py
@@ -0,0 +1,4 @@
+# requires python 2.x
+
+import sys
+print(sys.version)
diff --git a/src/testdir/pyxfile/py2_shebang.py b/src/testdir/pyxfile/py2_shebang.py
new file mode 100644
index 0000000..13bfc49
--- /dev/null
+++ b/src/testdir/pyxfile/py2_shebang.py
@@ -0,0 +1,4 @@
+#!/usr/bin/python2
+
+import sys
+print(sys.version)
diff --git a/src/testdir/pyxfile/py3_magic.py b/src/testdir/pyxfile/py3_magic.py
new file mode 100644
index 0000000..d4b7ee0
--- /dev/null
+++ b/src/testdir/pyxfile/py3_magic.py
@@ -0,0 +1,4 @@
+# requires python 3.x
+
+import sys
+print(sys.version)
diff --git a/src/testdir/pyxfile/py3_shebang.py b/src/testdir/pyxfile/py3_shebang.py
new file mode 100644
index 0000000..ec05808
--- /dev/null
+++ b/src/testdir/pyxfile/py3_shebang.py
@@ -0,0 +1,4 @@
+#!/usr/bin/python3
+
+import sys
+print(sys.version)
diff --git a/src/testdir/pyxfile/pyx.py b/src/testdir/pyxfile/pyx.py
new file mode 100644
index 0000000..261a651
--- /dev/null
+++ b/src/testdir/pyxfile/pyx.py
@@ -0,0 +1,2 @@
+import sys
+print(sys.version)
diff --git a/src/testdir/test_pyx2.vim b/src/testdir/test_pyx2.vim
new file mode 100644
index 0000000..50e57c3
--- /dev/null
+++ b/src/testdir/test_pyx2.vim
@@ -0,0 +1,74 @@
+" Test for pyx* commands and functions with Python 2.
+
+set pyx=2
+if !has('python')
+  finish
+endif
+
+let s:py2pattern = '^2\.[0-7]\.\d\+'
+let s:py3pattern = '^3\.\d\+\.\d\+'
+
+
+func Test_has_pythonx()
+  call assert_true(has('pythonx'))
+endfunc
+
+
+func Test_pyx()
+  redir => var
+  pyx << EOF
+import sys
+print(sys.version)
+EOF
+  redir END
+  call assert_match(s:py2pattern, split(var)[0])
+endfunc
+
+
+func Test_pyxdo()
+  pyx import sys
+  enew
+  pyxdo return sys.version.split("\n")[0]
+  call assert_match(s:py2pattern, split(getline('.'))[0])
+endfunc
+
+
+func Test_pyxeval()
+  pyx import sys
+  call assert_match(s:py2pattern, split(pyxeval('sys.version'))[0])
+endfunc
+
+
+func Test_pyxfile()
+  " No special comments nor shebangs
+  redir => var
+  pyxfile pyxfile/pyx.py
+  redir END
+  call assert_match(s:py2pattern, split(var)[0])
+
+  " Python 2 special comment
+  redir => var
+  pyxfile pyxfile/py2_magic.py
+  redir END
+  call assert_match(s:py2pattern, split(var)[0])
+
+  " Python 2 shebang
+  redir => var
+  pyxfile pyxfile/py2_shebang.py
+  redir END
+  call assert_match(s:py2pattern, split(var)[0])
+
+  if has('python3')
+    " Python 3 special comment
+    redir => var
+    pyxfile pyxfile/py3_magic.py
+    redir END
+    call assert_match(s:py3pattern, split(var)[0])
+
+    " Python 3 shebang
+    redir => var
+    pyxfile pyxfile/py3_shebang.py
+    redir END
+    call assert_match(s:py3pattern, split(var)[0])
+  endif
+endfunc
diff --git a/src/testdir/test_pyx3.vim b/src/testdir/test_pyx3.vim
new file mode 100644
index 0000000..64546b4
--- /dev/null
+++ b/src/testdir/test_pyx3.vim
@@ -0,0 +1,74 @@
+" Test for pyx* commands and functions with Python 3.
+
+set pyx=3
+if !has('python3')
+  finish
+endif
+
+let s:py2pattern = '^2\.[0-7]\.\d\+'
+let s:py3pattern = '^3\.\d\+\.\d\+'
+
+
+func Test_has_pythonx()
+  call assert_true(has('pythonx'))
+endfunc
+
+
+func Test_pyx()
+  redir => var
+  pyx << EOF
+import sys
+print(sys.version)
+EOF
+  redir END
+  call assert_match(s:py3pattern, split(var)[0])
+endfunc
+
+
+func Test_pyxdo()
+  pyx import sys
+  enew
+  pyxdo return sys.version.split("\n")[0]
+  call assert_match(s:py3pattern, split(getline('.'))[0])
+endfunc
+
+
+func Test_pyxeval()
+  pyx import sys
+  call assert_match(s:py3pattern, split(pyxeval('sys.version'))[0])
+endfunc
+
+
+func Test_pyxfile()
+  " No special comments nor shebangs
+  redir => var
+  pyxfile pyxfile/pyx.py
+  redir END
+  call assert_match(s:py3pattern, split(var)[0])
+
+  " Python 3 special comment
+  redir => var
+  pyxfile pyxfile/py3_magic.py
+  redir END
+  call assert_match(s:py3pattern, split(var)[0])
+
+  " Python 3 shebang
+  redir => var
+  pyxfile pyxfile/py3_shebang.py
+  redir END
+  call assert_match(s:py3pattern, split(var)[0])
+
+  if has('python')
+    " Python 2 special comment
+    redir => var
+    pyxfile pyxfile/py2_magic.py
+    redir END
+    call assert_match(s:py2pattern, split(var)[0])
+
+    " Python 2 shebang
+    redir => var
+    pyxfile pyxfile/py2_shebang.py
+    redir END
+    call assert_match(s:py2pattern, split(var)[0])
+  endif
+endfunc