Install for Ubuntu + fix multiple print of meshFormat in case of a multiple view file

Post/PViewDataGModelIO.cpp

@@ -156,9 +156,14 @@ bool PViewDataGModel::writeMSH(const std::string &fileName, bool binary, bool sa
     }
   }
   else{
-    if(multipleView)
+    if(multipleView){
       fp = fopen(fileName.c_str(), binary ? "ab" : "a");
-    else
+      if(!fp){
+        Msg::Error("Unable to open file '%s'", fileName.c_str());
+        return false;
+      }
+    }
+    else{
       fp = fopen(fileName.c_str(), binary ? "wb" : "w");
       if(!fp){
         Msg::Error("Unable to open file '%s'", fileName.c_str());
@@ -173,6 +178,7 @@ bool PViewDataGModel::writeMSH(const std::string &fileName, bool binary, bool sa
       }
       fprintf(fp, "$EndMeshFormat\n");
     }
+  }
 
   if(haveInterpolationMatrices()){
     fprintf(fp, "$InterpolationScheme\n");