Review OSError exceptions handling (#1080)

- Replace obsolete `IOError` (Python 2) with `OSError`,
  cf https://docs.python.org/3/library/exceptions.html#OSError.
- Improve `OSError` catches at different places, simplifying
  the code.

httpie/cli/argparser.py

@@ -176,7 +176,7 @@ class HTTPieArgumentParser(argparse.ArgumentParser):
             self.args.output_file.seek(0)
             try:
                 self.args.output_file.truncate()
-            except IOError as e:
+            except OSError as e:
                 if e.errno == errno.EINVAL:
                     # E.g. /dev/null on Linux.
                     pass

httpie/cli/argtypes.py

@@ -180,8 +180,8 @@ def readable_file_arg(filename):
     try:
         with open(filename, 'rb'):
             return filename
-    except IOError as ex:
-        raise argparse.ArgumentTypeError(f'{filename}: {ex.args[1]}')
+    except OSError as ex:
+        raise argparse.ArgumentTypeError(f'{ex.filename}: {ex.strerror}')
 
 
 def parse_format_options(s: str, defaults: Optional[dict]) -> dict:

httpie/cli/requestitems.py

@@ -106,7 +106,7 @@ def process_file_upload_arg(arg: KeyValueArg) -> Tuple[str, IO, str]:
     mime_type = parts[1] if len(parts) > 1 else None
     try:
         f = open(os.path.expanduser(filename), 'rb')
-    except IOError as e:
+    except OSError as e:
         raise ParseError(f'{arg.orig!r}: {e}')
     return (
         os.path.basename(filename),
@@ -139,7 +139,7 @@ def load_text_file(item: KeyValueArg) -> str:
     try:
         with open(os.path.expanduser(path), 'rb') as f:
             return f.read().decode()
-    except IOError as e:
+    except OSError as e:
         raise ParseError(f'{item.orig!r}: {e}')
     except UnicodeDecodeError:
         raise ParseError(