Fix gitian-build.py --verify option

The gitian-builder/bin/gverify script returns the exit code 1 if a
signature verification ends with 'BAD SIGNATURE' or 'MISMATCH' by
design. This commit allows to see the verification results for all
signatures without a premature fail of the gitian-build.py script.

contrib/gitian-build.py

@@ -118,20 +118,36 @@ def sign():
 
 def verify():
     global args, workdir
+    rc = 0
     os.chdir('gitian-builder')
 
     print('\nVerifying v'+args.version+' Linux\n')
-    subprocess.check_call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-linux', '../bitcoin/contrib/gitian-descriptors/gitian-linux.yml'])
+    if subprocess.call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-linux', '../bitcoin/contrib/gitian-descriptors/gitian-linux.yml']):
+        print('Verifying v'+args.version+' Linux FAILED\n')
+        rc = 1
+
     print('\nVerifying v'+args.version+' Windows\n')
-    subprocess.check_call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-win-unsigned', '../bitcoin/contrib/gitian-descriptors/gitian-win.yml'])
+    if subprocess.call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-win-unsigned', '../bitcoin/contrib/gitian-descriptors/gitian-win.yml']):
+        print('Verifying v'+args.version+' Windows FAILED\n')
+        rc = 1
+
     print('\nVerifying v'+args.version+' MacOS\n')
-    subprocess.check_call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-osx-unsigned', '../bitcoin/contrib/gitian-descriptors/gitian-osx.yml'])
+    if subprocess.call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-osx-unsigned', '../bitcoin/contrib/gitian-descriptors/gitian-osx.yml']):
+        print('Verifying v'+args.version+' MacOS FAILED\n')
+        rc = 1
+
     print('\nVerifying v'+args.version+' Signed Windows\n')
-    subprocess.check_call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-win-signed', '../bitcoin/contrib/gitian-descriptors/gitian-win-signer.yml'])
+    if subprocess.call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-win-signed', '../bitcoin/contrib/gitian-descriptors/gitian-win-signer.yml']):
+        print('Verifying v'+args.version+' Signed Windows FAILED\n')
+        rc = 1
+
     print('\nVerifying v'+args.version+' Signed MacOS\n')
-    subprocess.check_call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-osx-signed', '../bitcoin/contrib/gitian-descriptors/gitian-osx-signer.yml'])
+    if subprocess.call(['bin/gverify', '-v', '-d', '../gitian.sigs/', '-r', args.version+'-osx-signed', '../bitcoin/contrib/gitian-descriptors/gitian-osx-signer.yml']):
+        print('Verifying v'+args.version+' Signed MacOS FAILED\n')
+        rc = 1
 
     os.chdir(workdir)
+    return rc
 
 def main():
     global args, workdir
@@ -237,7 +253,7 @@ def main():
         os.chdir('gitian.sigs')
         subprocess.check_call(['git', 'pull'])
         os.chdir(workdir)
-        verify()
+        sys.exit(verify())
 
 if __name__ == '__main__':
     main()