add unit tests and fix exception clause compatibility

Exceptions are now compatible with both python 2.4 and 3.3,
and we have unit tests to detect regressions.

The syntax for capturing exceptions changed in python 3, but
we need to continue supporting python 2.4 syntax since many
people use tito on RHEL 5, which has python 2.4.

http://docs.python.org/dev/howto/pyporting.html#capturing-the-currently-raised-exception

HACKING

@@ -9,6 +9,17 @@ See http://docs.python.org/dev/howto/pyporting.html
 and http://python3porting.com/differences.html
 for tips on writing portable Python code.
 
+In particular, you must capture exceptions in a way that's
+compatible with both python 2.4 and 3.x. For example:
+
+    try:
+        raise Exception()
+    except Exception:
+        import sys
+        exc = sys.exc_info()[1]
+        # Current exception is 'exc'.
+        pass
+
 
 Tests
 -----

src/tito/builder/main.py

@@ -227,13 +227,15 @@ class BuilderBase(object):
         except (KeyboardInterrupt, SystemExit):
             print ""
             exit(1)
-        except RunCommandException, err:
+        except RunCommandException:
+            err = sys.exc_info()[1]
             msg = str(err)
             if (re.search('Failed build dependencies', err.output)):
                 msg = "Please run 'yum-builddep %s' as root." % \
                     find_spec_file(self.relative_project_dir)
             error_out('%s' % msg)
-        except Exception, err:
+        except Exception:
+            err = sys.exc_info()[1]
             error_out('%s' % str(err))
         print(output)
         files_written = find_wrote_in_rpmbuild_output(output)

src/tito/cli.py

@@ -709,7 +709,8 @@ class TagModule(BaseCliModule):
 
         try:
             return tagger.run(self.options)
-        except TitoException, e:
+        except TitoException:
+            e = sys.exc_info()[1]
             error_out(e.message)
 
     def _validate_options(self):

src/tito/release.py

@@ -16,6 +16,7 @@ Code for submitting builds for release.
 
 import copy
 import os
+import sys
 import commands
 import tempfile
 import subprocess
@@ -454,7 +455,7 @@ class YumRepoReleaser(RsyncReleaser):
             if artifact.endswith(".rpm") and not artifact.endswith(".src.rpm"):
                 try:
                     header = self._read_rpm_header(rpm_ts, artifact)
-                except rpm.error, e:
+                except rpm.error:
                     continue
                 self.new_rpm_dep_sets[header['name']] = header.dsOfHeader()
 
@@ -467,7 +468,8 @@ class YumRepoReleaser(RsyncReleaser):
             full_path = os.path.join(temp_dir, filename)
             try:
                 hdr = self._read_rpm_header(rpm_ts, full_path)
-            except rpm.error, e:
+            except rpm.error:
+                e = sys.exc_info()[1]
                 print "error reading rpm header in '%s': %s" % (full_path, e)
                 continue
             if hdr['name'] in self.new_rpm_dep_sets:

test/unit/pep8-tests.py

@@ -64,3 +64,23 @@ class TestPep8(TitoUnitTestFixture):
 
         self.assertEqual(result, 0,
             "Found PEP8 errors that may break your code in Python 3.")
+
+
+class UglyHackishTest(TitoUnitTestFixture):
+    def setUp(self):
+        TitoUnitTestFixture.setUp(self)
+        os.chdir(REPO_DIR)
+
+    def test_exceptions_2_dot_4(self):
+        # detect 'except rpm.error as e:'
+        regex = "'^[[:space:]]*except .* as .*:'"
+        cmd = "find . -type f -regex '.*\.py$' -exec egrep %s {} + | wc -l" % regex
+        result = int(getoutput(cmd))
+        self.assertEqual(result, 0, "Found except clause not supported in Python 2.4")
+
+    def test_exceptions_3(self):
+        # detect 'except rpm.error, e:'
+        regex = "'^[[:space:]]*except [^,]+,[[:space:]]*[[:alpha:]]+:'"
+        cmd = "find . -type f -regex '.*\.py$' -exec egrep %s {} + | wc -l" % regex
+        result = int(getoutput(cmd))
+        self.assertEqual(result, 0, "Found except clause not supported in Python 3")