Add error response

lantern/error.py

@@ -0,0 +1,12 @@
+from jinja2 import Template
+from sanic.response import html
+import os
+
+
+TEMPLATE = os.path.join(os.path.dirname(__file__), 'templates', 'error.html')
+
+
+def error_response(error_str):
+    with open(TEMPLATE) as f:
+        template = Template(f.read())
+    return html(template.render(error=error_str), status=500)

lantern/handle.py

@@ -8,13 +8,12 @@ Result = namedtuple('Result', ['exit_code', 'html', 'error'])
 
 def execute_handle(executable, request_data):
     input_data = json.dumps(request_data).encode('utf-8')
-    cmd = subprocess.run(executable, input=input_data, stdout=subprocess.PIPE)
+    try:
+        cmd = subprocess.run(executable, input=input_data, stdout=subprocess.PIPE)
+    except Exception as e:
+        return Result(1, None, str(e))
     return Result(
         cmd.returncode,
         cmd.stdout.decode('utf-8'),
         cmd.stderr.decode('utf-8') if cmd.stderr is not None else None
     )
-
-
-def get_http_status_code(exit_code):
-    return 200 if exit_code == 0 else 500

lantern/route.py

@@ -1,9 +1,13 @@
 from sanic.response import html
-from lantern.handle import execute_handle, get_http_status_code
+from lantern.handle import execute_handle
+from lantern.error import error_response
 import os
 
 
 async def main_route(request, path=None):
     handle = os.path.join(os.path.dirname(__file__), 'test_handle.py')
     result = execute_handle(handle, {})
-    return html(result.html, status=get_http_status_code(result.exit_code))
+    if result.exit_code != 0:
+        return error_response(result.error)
+
+    return html(result.html, status=200)

lantern/templates/error.html

@@ -0,0 +1,2 @@
+<h1>Error</h1>
+<p>{{ error }}</p>

setup.py

@@ -6,7 +6,8 @@ setup(
     version="1.0",
     install_requires=[
         "sanic==0.4.1",
-        "sanic-useragent==0.1.2"
+        "sanic-useragent==0.1.2",
+        "Jinja2==2.9.6"
     ],
     entry_points="""
         [console_scripts]