convert/svn: better error when hg cannot call itself (issue1838)

hgext/convert/subversion.py

@@ -115,7 +115,11 b' class logstream(object):'
 
     def __iter__(self):
         while True:
-            entry = pickle.load(self._stdout)
+            try:
+                entry = pickle.load(self._stdout)
+            except EOFError:
+                raise util.Abort(_('Mercurial failed to run itself, check'
+                                   ' hg executable is in PATH'))
             try:
                 orig_paths, revnum, author, date, message = entry
             except:

tests/test-convert-svn-branches

@@ -28,3 +28,7 b" hg glog --template 'branch={branches} {r"
 hg branches | sed 's/:.*/:/'
 hg tags -q
 cd ..
+
+echo '% test hg failing to call itself'
+HG=foobar hg convert svn-repo B-hg 2>&1 | grep -v foobar
+

tests/test-convert-svn-branches.out

@@ -48,3 +48,6 b' default 10:'
 old                            9:
 old2                           8:
 tip
+% test hg failing to call itself
+initializing destination B-hg repository
+abort: Mercurial failed to run itself, check hg executable is in PATH