Launch validation (#414)

* WIP

* Cleanup

* Validation

* typo

* Max category limit 100 -> 500

server/app/util/errors.py

@@ -0,0 +1,43 @@
+class FilterError(Exception):
+    """
+    Raised when filter is malformed
+    """
+
+    def __init__(self, message):
+        self.message = message
+
+
+class InteractiveError(Exception):
+    """
+    Raised when computation would exceed interactive time
+    """
+
+    def __init__(self, message):
+        self.message = message
+
+
+class MimeTypeError(Exception):
+    """
+    Raised when incompatible MIME type selected
+    """
+
+    def __init__(self, message):
+        self.message = message
+
+
+class PrepareError(Exception):
+    """
+    Raised when data is misprepared
+    """
+
+    def __init__(self, message):
+        self.message = message
+
+
+class ScanpyFileError(Exception):
+    """
+    Raised when file loaded into scanpy is misformatted
+    """
+
+    def __init__(self, message):
+        self.message = message