ob-python.el: Fix multiline strings in non-session :results value

* lisp/ob-python.el (org-babel-python-evaluate-external-process): Use
functions from python.el to indent lines, avoiding multiline strings.
* testing/lisp/test-ob-python.el (test-ob-python/multiline-var): Set
test as expected to succeed.
(test-ob-python/multiline-str): Add test for multiline string in body.
(test-ob-python/header-var-assignment): Test that :var is in correct
scope and can be assigned to.

cf. https://orgmode.org/list/87tv009l9a.fsf@gmail.com/#t

lisp/ob-python.el

@@ -33,6 +33,8 @@
 (declare-function py-shell "ext:python-mode" (&rest args))
 (declare-function py-toggle-shells "ext:python-mode" (arg))
 (declare-function run-python "ext:python" (&optional cmd dedicated show))
+(declare-function python-syntax-context "ext:python" (&rest args))
+(declare-function python-indent-shift-right "ext:python" (&rest args))
 
 (defvar org-babel-tangle-lang-exts)
 (add-to-list 'org-babel-tangle-lang-exts '("python" . "py"))
@@ -296,11 +298,17 @@ last statement in BODY, as elisp."
 			(if (member "pp" result-params)
 			    org-babel-python-pp-wrapper-method
 			  org-babel-python-wrapper-method)
-			(mapconcat
-			 (lambda (line) (format "\t%s" line))
-			 (split-string (org-remove-indentation (org-trim body))
-				       "[\r\n]")
-			 "\n")
+			(with-temp-buffer
+			  (require 'python)
+			  (python-mode)
+			  (insert body)
+			  (goto-char (point-min))
+			  (while (not (eobp))
+			    (unless (python-syntax-context 'string)
+			      (python-indent-shift-right (line-beginning-position)
+							 (line-end-position)))
+			   (forward-line 1))
+			 (buffer-string))
 			(org-babel-process-file-name tmp-file 'noquote))))
 		     (org-babel-eval-read-file tmp-file))))))
     (org-babel-result-cond result-params

testing/lisp/test-ob-python.el

@@ -174,7 +174,6 @@ _ = 'failure'
 	    (org-babel-execute-src-block)))))
 
 (ert-deftest test-ob-python/multiline-var ()
-  :expected-result :failed
   (should
    (equal "a\nb\nc"
 	  (org-test-with-temp-text "#+begin_src python :var text=\"a\\nb\\nc\"
@@ -182,6 +181,25 @@ return text
 #+end_src"
 	    (org-babel-execute-src-block)))))
 
+(ert-deftest test-ob-python/multiline-str ()
+  (should
+   (equal "a\nb\nc"
+	  (org-test-with-temp-text "#+begin_src python
+text=\"a\\nb\\nc\"
+return text
+#+end_src"
+	    (org-babel-execute-src-block)))))
+
+(ert-deftest test-ob-python/header-var-assignment ()
+  (should
+   (equal "success"
+	  (org-test-with-temp-text "#+begin_src python :var text=\"failure\"
+text
+text=\"success\"
+return text
+#+end_src"
+	    (org-babel-execute-src-block)))))
+
 (provide 'test-ob-python)
 
 ;;; test-ob-python.el ends here