Revert "Tests: speed up render tests by running multiple in the same process"

This makes finding the crashing tests harder, reverting until there is a
better solution.

This reverts commit 93901e7f0a.

tests/python/opengl_draw_tests.py

@@ -31,48 +31,41 @@ if inside_blender:
     sys.exit(0)
 
 
-def render_files(filepaths, output_filepaths):
-    errors = []
+def render_file(filepath, output_filepath):
+    command = (
+        BLENDER,
+        "--no-window-focus",
+        "--window-geometry",
+        "0", "0", "1024", "768",
+        "-noaudio",
+        "--factory-startup",
+        "--enable-autoexec",
+        filepath,
+        "-P",
+        os.path.realpath(__file__),
+        "--",
+        output_filepath)
 
-    for filepath, output_filepath in zip(filepaths, output_filepaths):
-        command = (
-            BLENDER,
-            "--no-window-focus",
-            "--window-geometry",
-            "0", "0", "1024", "768",
-            "-noaudio",
-            "--factory-startup",
-            "--enable-autoexec",
-            filepath,
-            "-P",
-            os.path.realpath(__file__),
-            "--",
-            output_filepath)
-
-        error = None
-        try:
-            # Success
-            output = subprocess.check_output(command)
-            if VERBOSE:
-                print(output.decode("utf-8"))
-        except subprocess.CalledProcessError as e:
-            # Error
-            if os.path.exists(output_filepath):
-                os.remove(output_filepath)
-            if VERBOSE:
-                print(e.output.decode("utf-8"))
-            error = "CRASH"
-        except BaseException as e:
-            # Crash
-            if os.path.exists(output_filepath):
-                os.remove(output_filepath)
-            if VERBOSE:
-                print(e)
-            error = "CRASH"
-
-        errors.append(error)
-
-    return errors
+    try:
+        # Success
+        output = subprocess.check_output(command)
+        if VERBOSE:
+            print(output.decode("utf-8"))
+        return None
+    except subprocess.CalledProcessError as e:
+        # Error
+        if os.path.exists(output_filepath):
+            os.remove(output_filepath)
+        if VERBOSE:
+            print(e.output.decode("utf-8"))
+        return "CRASH"
+    except BaseException as e:
+        # Crash
+        if os.path.exists(output_filepath):
+            os.remove(output_filepath)
+        if VERBOSE:
+            print(e)
+        return "CRASH"
 
 
 def create_argparse():
@@ -99,7 +92,7 @@ def main():
 
     from modules import render_report
     report = render_report.Report("OpenGL Draw Test Report", output_dir, idiff)
-    ok = report.run(test_dir, render_files)
+    ok = report.run(test_dir, render_file)
 
     sys.exit(not ok)