Adjust exception formatting

scrapy/core/engine.py

@@ -169,7 +169,8 @@ def _next_request_from_scheduler(self, spider):
     def _handle_downloader_output(self, response, request, spider):
         if not isinstance(response, (Request, Response, Failure)):
             raise TypeError(
-                "Incorrect type: expected Request, Response or Failure, got %s" % type(response)
+                "Incorrect type: expected Request, Response or Failure, got %s: %r"
+                % (type(response), response)
             )
         # downloader middleware can return requests (for example, redirects)
         if isinstance(response, Request):
@@ -239,7 +240,8 @@ def _download(self, request, spider):
         def _on_success(response):
             if not isinstance(response, (Response, Request)):
                 raise TypeError(
-                    "Incorrect type: expected Response or Request, got %s" % type(response)
+                    "Incorrect type: expected Response or Request, got %s: %r"
+                    % (type(response), response)
                 )
             if isinstance(response, Response):
                 response.request = request  # tie request to response received

scrapy/core/scraper.py

@@ -125,7 +125,8 @@ def _scrape(self, response, request, spider):
         callback/errback"""
         if not isinstance(response, (Response, Failure)):
             raise TypeError(
-                "Incorrect type: expected Response or Failure, got %s" % type(response)
+                "Incorrect type: expected Response or Failure, got %s: %r"
+                % (type(response), response)
             )
 
         dfd = self._scrape2(response, request, spider)  # returns spider's processed output

scrapy/pipelines/files.py

@@ -107,7 +107,7 @@ def __init__(self, uri):
             from boto.s3.connection import S3Connection
             self.S3Connection = S3Connection
         if not uri.startswith("s3://"):
-            raise ValueError("Incorrect URI scheme in %s, expected s3" % uri)
+            raise ValueError("Incorrect URI scheme in %s, expected 's3'" % uri)
         self.bucket, self.prefix = uri[5:].split('/', 1)
 
     def stat_file(self, path, info):
@@ -267,8 +267,8 @@ class FTPFilesStore:
     USE_ACTIVE_MODE = None
 
     def __init__(self, uri):
-        if not uri.startswith('ftp://'):
-            raise ValueError("Incorrect URI scheme in %s, expected ftp" % uri)
+        if not uri.startswith("ftp://"):
+            raise ValueError("Incorrect URI scheme in %s, expected 'ftp'" % uri)
         u = urlparse(uri)
         self.port = u.port
         self.host = u.hostname

scrapy/utils/iterators.py

@@ -130,7 +130,10 @@ def _body_or_str(obj, unicode=True):
     expected_types = (Response, str, bytes)
     if not isinstance(obj, expected_types):
         expected_types_str = " or ".join(t.__name__ for t in expected_types)
-        raise TypeError("obj must be %s, not %s" % (expected_types_str, type(obj).__name__))
+        raise TypeError(
+            "Object %r must be %s, not %s"
+            % (obj, expected_types_str, type(obj).__name__)
+        )
     if isinstance(obj, Response):
         if not unicode:
             return obj.body